GIFT  OF 

PROF.  W.B.  RISING 


INTRODUCTION 


TO 


CHEMICAL-TECHNICAL 
ANALYSIS 


BY 


PROF.  F.  ULZER  AND  DR.  A.  FRAENKEL 

DIRECTORS  OF  THE  TESTING  LABORATORY  OF  THE  ROYAL  TECHNOLOGICAL  MUSEUM, 

IN  VIENNA 


(AUTHORIZED  TRANSLATION) 


WITH   APPENDIX   BY  THE   TRANSLATOR 


HERMANN  FLECK,  NAT.  Sc.  D. 

INSTRUCTOR    IN    CHEMISTRY,  UNIVERSITY    OF    PENNSYLVANIA 


PHILADELPHIA 

P.  BLAKISTON'S    SON   &    CO. 

1012  WALNUT   STREET 

1898 


II  lo  2. 


COPYRIGHT,  1898,  BY 
P.  BLAKISTON'S  SON  &  CO. 


PRESS  OF 

an  &  Co., 


Preface. 


IT  is  generally  conceded  that  it  is  advisable  to  give  students  of 
chemistry  as  broad  an  experience  as  possible  in  the  use  of  analytical 
methods,  in  order  to  have  them  acquire  skill  in  manipulation  and  to 
acquaint  them  with  the  important  bearing  of  chemical  analysis. 

This  experience  can,  in  a  great  measure,  be  obtained  by  supple- 
menting the  usual  preparatory  courses  in  gravimetric  and  volu- 
metric analysis  with  instruction  in  the  execution  of  methods  which 
are  being  constantly  applied  in  the  analysis  of  industrial  products. 
The  authors  of  this  book  have  had  much  experience  in  teaching 
chemical-technical  analysis,  and  in  the  following  pages  have  pre- 
sented many  methods  of  this  description  in  a  series  of  examples, 
selected  from  a  variety  of  products.  They  have  been  very  fortunate  in 
their  choice,  and  have  undoubtedly  done  much  to  assist  the  earnest 
student. 

The  conviction  that  a  course  of  this  character  would  be  wel- 
comed by  English-speaking  students,  and  helpful  not  only  to  them 
but  also  to  many  who  are  already  engaged  in  industrial  pursuits,  has 
led  the  translator  to  publish  the  little  volume  in  its  present  form.  He 
has  not  edited  the  text,  but  has  taken  the  liberty  to  add  an  appendix, 
in  which  are  incorporated  additional  examples  which  actual  labor- 
atory testing  has  shown  to  be  highly  instructive,  as  well  as  exceed- 
ingly valuable,  in  the  direction  of  imparting  skill  in  manipulation. 

In  this  connection,  too,  the  translator  would  take  occasion  to 
acknowledge  his  great  indebtedness  to  Mr.  Walter  T.  Taggart, 
B.  S.,  for  valuable  assistance  rendered  in  the  reading  of  the  proof 
and  the  preparation  of  the  index.  H.  F. 

(iii  ) 

237357 


Table  of  Contents. 


PAGE 

I.  Products  of  Technical  Chemistry, i 

1.  Iron  Pyrites, I 

2.  Pyrite  Residuum,         .  •         •       3 

3.  Sulphuric  Acid,  ....          ......       4 

4.  Fuming  Sulphuric  Acid  and  Anhydride, 5 

5.  Nitroso  Acid  (Nitrated  Acid),      .  7 

6.  Brine, 1 1 

7.  Crude  Hydrochloric  Acid,  .         .         .          .          .         .         .         .12 

8.  Soda,  ;         .         .         .         .  .         .         .         .  13 

9.  Sodium  Aluminate,      .          .          .          .         .         .'•'•.         .         .17 

10.  Weldon  Mud, 18 

11.  Boiler- Water, 20 

12.  Fuel, 27 

13.  Furnace  Gases,   ..........     32 

II.  Cement  and  Clay,        ...  ,35 

1.  Lime,  .         .         .  35 

2.  Marl, 37 

3-   Clay, 39 

A.  Empirical-Technical  Analysis,    ......     40 

B.  Rational  Analysis,       ........     42 

C.  Analysis  by  Mechanical  Means  (Suspension),     .         .         -43 

D.  Pyrometric  Tests,        .         .          .         .         .         .          .          -45 

III.  Metallurgical  Industry, 51 

1.  Iron,  .          .         .          .         .         .         .          .         .         .          .          •  51 

2.  Zinc  Blende, 57 

3.  Zinc  Dust,  ...........  59 

4.  Crude  and  Refined  Copper, 60 

IV.  Alloys, 68 

1.  Phosphor- Bronze,         .........  68 

2.  White  Metal, 69 

3.  Iron  Alloys,          ..........  70 

V.  Fertilizers, 72 

1.  Phosphate  Fertilizers, 75 

2.  Potassium  Fertilizers,  .........     77 

3.  Nitrogenous  Fertilizers,        ........     78 

4.  Mixed  Fertilizers,         .          .         .         .         .          .         .         .         .78 

(v) 


VI  TABLE    OF    CONTENTS. 

PAGE 

VI.  Sugar  Industry, 79 

1.  Beets, 82 

2.  Beet  Juice,  Thin  Juice,         .                   84 

3.  Crude  Sugar,  Filling  Material,  Green  Syrup,  Molasses,        .         .  84 

4.  Press  Cake, 91 

5.  Lime  Saccharate,         .........  91 

6.  Bone  Black, .91 

VII.  Fermentation  Industries, 95 

1.  Raw  Products  Containing  Starch, 95 

2.  Starch, 99 

3.  Malt, 100 

4.  Yeast,          . 103 

5.  Spirits, 105 

6.  Methyl  Alcohol  (Wood  Spirit), 107 

VIII.  Fats,  Waxes,  Mineral  Oils, .  109 

A.  F'ats, 109 

1.  General  Methods, 109 

2.  Classification  of  Fats, 114 

3.  Investigation  of  a  Few  Common  Fats,     .         .         .         .117 

B.  Waxes, .         .         .         .121 

1.  Vegetable  and  Animal  Waxes,         .         .         .         .         .121 

2.  Mineral  Waxes, .         .125 

C.  Mineral  Oils, 125 

1.  Mineral  Lubricants,          .          .         .         .         .         .         .126 

2.  Petroleum  (Illuminating  Oil), 129 

3.  Gas  Oil, .         .         .   131 

D.  Products  of  the  Fat  Industry, 131 

1.  Materials  Used  in  Oiling  Wool,       .         .         .         .         .   131 

2.  Soaps, 133 

3.  Turkey-Red  Oil, .138 

4.  Glycerin, 140 

IX.  Mordants  and  Tanning  Materials,  .......   143 

A.  Mordants, 143 

1.  Alumina  Mordants, 143 

2.  Chromium  Mordants, 145 

3.  Iron  Mordants,        ........  146 

4.  Tin  Mordants, 146 

5.  Antimony  Mordants, 147 

6.  Copper  Mordants,   .         .         .         .         .         .         .         .  147 

B.  Tanning  Materials,  . 147 

1.  Tanning  Extracts,  .          .         .         .         .          .         .         .148 

2.  Raw  Products, 149 

X.  Textile  and  Dyeing  Industries, 151 

1.  Textile  Fibers, 151 

2.  Bleaching  Materials, 153 


TABLE    OF    CONTENTS.  Vli 

PAGE 

3.  Sizing  Materials, 154 

4.  Finishing  Materials,    .         .          .          .         .         .         .         .         .156 

5.  Dye-Stuffs, .158 

XI.  Products  of  the  Coal-Tar  Industry,         ......  165 

1.  Crude  Benzene,  ..........  165 

2.  Crude  Xylol, 165 

3.  Crude  Anthracene,       .         .         .         .         .         .         .         .         .166 

4.  Crude  Carbolic  Acid 167 

5.  Dimethyl  Aniline,        .........  168 

Appendix, 

A.   White  Paint  (White  Lead), 169 

13.    Manganese  Dioxide,  Bleaching  Lime,  Etc.,          ....  169 

1.  Manganese  Dioxide,       ........   169 

2.  Bleaching  Lime,     .........   172 

3.  Hydrogen  Peroxide  and  Permanganate,  .         .         .         .172 

C.  Asphalt  and  Asphaltic  Substances,       .          .         .         ....   172 

D.  Food  Stuffs, 174 

1.  Milk, 174 

2.  Butter, .'77 

3-  Tea, 178 

4.  Coffee, .          .          .  179 

5.  Cocoa  and  Chocolate,     .          .         .          .         .         .         .         .180 

6.  Flour  and  Other  Cereals, 182 

7.  Pepper, 183 


Abbreviations. 

Be.  =r  Beaume. 

c.c.  =  Cubic  Centimeter. 

C.  —  Celsius. 
Cone.  —  Concentrated. 

F.  =  Fahrenheit. 
Gr.  =  Gram, 
m.m.    —  Millimeter. 
Temperature  (Celsius  is  understood  unless  otherwise  indicated.) 


I.  Products  of  Technical  Chemistry. 


IN  this  chapter  a  selection  is  made  from  the  most  important  in- 
dustrial chemical  products  as  well  as  from  the  raw  materials  used 
therein,  and  a  description  of  the  quantitative  examination  of  the 
same  is  given.  The  methods  described  are  followed  by  those  em- 
ployed in  the  analysis  of  water,  coal  and  furnace  gas. 

1.  Iron  Pyrites. 

The  most  important  determination  is  that  of  sulphur.  The  error 
must  not  exceed  .  i  per  cent.  In  addition  a  water  determination  is 
usually  conducted,  and  less  frequently  estimations  of  copper  and 
arsenic. 

(#)  Sulphur.  Following  the  method  of  Lunge,  which  is  adopted 
in  the  German  Le  Blanc  soda  factories,  .  5  gram  of  finely-divided  and 
bolted  pyrite  is  covered  with  10  c.c.  of  a  mixture  of  3  vols.  nitric 
acid  (sp.  gr.  1.4)  and  i  vol.  fuming  hydrochloric  acid  in  an  Erlen- 
meyer  flask.  A  funnel  is  inserted  and  the  contents  are  warmed 
until  reaction  begins.  The  flask  is  then  removed  from  the  water- 
bath,  and  the  reaction  proceeds  of  its  own  accord  until  nearly 
complete.  The  contents  are  warmed  anew  until  the  reaction  is 
finished.  Solution  takes  place  in  about  ten  minutes.  Only  small 
quantities  of  colorless  substances,  silica,  barium  sulphate,  lead  sul- 
phate, etc.,  but  neither  dark  particles  nor  sulphur,  may  remain  un- 
dissolved.  The  solution  is  evaporated  to  dryness  in  a  porcelain 
dish  with  an  excess  of  hydrochloric  acid ;  the  residue  is  moistened 
with  a  few  drops  of  hydrochloric  acid,  taken  up  with  hot  water,  and 
filtered.  In  the  filtrate,  at  a  temperature  of  60-70°  the  iron  is 
precipitated  with  a  slight  excess  of  ammonia.  The  precipitate  is 
thrown  on  a  sufficiently  porous  filter  and  washed  with  hot  water 
until  i  c.c.  filtrate  remains  perfectly  clear  for  several  minutes  on 
addition  of  barium  chloride  solution.  The  filtrate  is  acidified  with 
hydrochloric  acid,  brought  to  boiling,  and  the  sulphuric  acid  is 

1 


2  CHEMICAL-TECHNICAL    ANALYSIS. 

precipitated  with  about  20  c.c.  of  a  hot  solution  of  barium  chloride 
(10  per  cent.).  The  remainder  of  the  analysis  is  conducted  in  the 
usual  manner.  The  sulphur  in  pyrite  varies  between  46  and  52 
per  cent.  Spanish  and  Norwegian  pyrites  are  characterized  by 
their  high  percentage  of  sulphur. 

(^)  Moisture.  About  10  grs.  sample  are  dried  to  constant 
weight  in  an  air-bath  at  105°.  Usually  four  hours  are  required  for 
this  operation. 

(V)  Copper.  According  to  the  procedure  of  Duisberger-Hiitte,* 
five  grams  of  the  finely-ground  and  previously  dried  (100°)  min- 
eral are  gradually  brought  into  an  inclined  Erlenmeyer  flask  con- 
taining 60  c.c.  nitric  acid  (sp.  gr.  1.2).  As  soon  as  the  ensuing 
violent  reaction  ceases  the  flask  is  heated  and  the  contents  are  evap- 
orated until  sulphuric  acid  vapors  are  evolved.  The  dry  residue  is 
then  dissolved  in  50  c.c.  HC1  (sp.gr.,  1.19),  2  grams  sodium 
hypophosphite  dissolved  in  5  c.c.  water  are  added,  and  the  liquid  is 
boiled  to  remove  the  arsenic  and  reduce  the  iron.  An  excess  of 
concentrated  HC1  is  now  added,  followed  by  300  c.c.  hot  water,  and 
hydrogen-sulphide  gas  to  saturation.  The  precipitate  is  filtered  off 
and  thoroughly  washed.  The  filter  is  broken  with  a  glass  rod,  and 
the  contents  are  washed  back  into  the  precipitates  in  flask.  The 
adhering  particles  on  the  filter,  together  with  the  main  portion  of 
the  precipitate,  are  dissolved  in  nitric  acid  and  the  solution  is 
evaporated  to  dryness  on  a  water-bath.  The  residue  is  treated  again 
with  nitric  acid  and  water,  neutralized  with  ammonia,  and  a  slight 
excess  of  dilute  sulphuric  acid  is  added.  After  cooling,  the  solu- 
tion is  filtered,  the  flask  and  filter  are  washed  with  wrater  containing 
sulphuric  acid,  and  the  copper  is  determined  electrolytically  in  the 
filtrate  after  adding  3  to  8  c.c.  nitric  acid,  or  gravimetrically  with- 
out the  addition  of  nitric  acid  as  cuprous  sulphide.  From  the  per- 
centage found,  .01  is  deducted  for  bismuth  and  antimony.  Any 
appreciable  amount  of  copper  in  pyrite  is  easily  recognized  during 
the  sulphur  determination  by  the  blue  ammoniacal  filtrate. 

(d}  Arsenic.  (Method  of  Reich,  modified  by  McCay.)  0.5 
gram  of  pyrite  is  dissolved  in  a  porcelain  crucible  with  nitric  acid. 
The  free  acid  is  volatilized,  4  grams  soda  are  added,  and  the  mass  is 

*  Taschenbuch  fur  die  Soda-,  Pottasche-  und  Ammoniakfabrikation  von  Dr.  G. 
Lunge.  2  Aufl. 


PYRITE    RESIDUUM.  3 

thoroughly  dried  on  a  sand-bath,  when  4  grams  saltpetre  are  added 
and  the  contents  are  heated  to  quiet  fusion  for  ten  minutes.  The 
fusion  is  lixiviated  with  a  small  quantity  of  hot  water,  and  to  the 
filtered  solution  sufficient  nitric  acid  is  added  to  slightly  acidify, 
after  which  the  liberated  carbonic  acid  is  expelled  by  boiling. 
Silver  nitrate  is  now  added,  and  the  solution  is  carefully  neutralized 
with  weak  ammonia.  All  arsenic  is  obtained  in  the  form  of  silver 
arsenate,  which  is  dissolved  in  dilute  nitric  acid.  The  solution  is 
either  evaporated  in  a  platinum  capsule,  dried  and  weighed  as  sil- 
ver arsenate  ( Ag3  As  O4),  or  titrated  with  ammonium  sulpho -cyanide 
according  to  the  method  of  Volhard. 

2.  Pyrite  Residuum. 

The  determination  of  sulphur  in  pyrite  residuum,  an  operation 
not  infrequently  required,  can  be  carried  out  under  the  directions 
given  in  Example  i,  except  that,  in  order  to  avoid  evolution  of 
hydrogen  sulphide,  solution  is  advantageously  effected  by  nitric 
acid  and  only  a  few  drops  of  hydrochloric  acid. 

Lunge*  recommends  for  this  purpose  the  following  method  : 
Exactly  2  grams  of  sodium-bicarbonate,  whose  strength  has  been 
previously  estimated  by  titration,  are  thoroughly  mixed  with  3.2 
grams  finely -divided  residuum  in  a  nickel  crucible  of  about  30  c.c. 
capacity.  The  mixture  is  heated  first  for  10  minutes  with  a  small 
flame  just  touching  the  bottom,  and  afterwards  for  15  minutes  with 
a  strong  flame,  without  allowing  the  mass  to  melt.  The  crucible 
should  be  covered  during  this  operation.  The  contents  are  poured 
out  into  a  porcelain  dish,  the  crucible  is  rinsed  with  water,  and 
treated  for  ten  minutes  with  a  concentrated  neutral  brine  in  order 
to  avoid  subsequent  escape  of  iron  oxide  through  the  filter.  The 
undissolved  portion  is  filtered  off  and  washed  until  the  filtrate 
ceases  to  give  an  alkaline  reaction.  After  cooling,  the  liquid  is 
titrated  back  with  normal  acid,  using  methyl-orange  as  an  indica- 
tor. The  difference  between  the  number  of  c.c.  hydrochloric  acid 
(# )  necessary  to  neutralize  2  grs.  bicarbonate  and  the  number  of 
c.c.  (£)  used  in  back  titration,  multiplied  by  the  sulphur  equiva- 
lent (i  c.c.  in  acid  =  0.016  gr.  S)  gives  the  amount  of  sulphur 

*  Taschenbuch  fur  die  Sodafabrikation,  etc. 


4  CHEMICAL-TECHNICAL   ANALYSIS. 

present.     Using  the  above  amount  of  substance,  the  percentage  of 
sulphur  is  : 


3.  Sulphuric  Acid. 

A  quantitative  determination  of  the  impurities  is  seldom  made 
except,  for  example,  for  storage -battery  purposes.  The  qualitative 
tests  here  given  for  detection  of  sulphurous  acid,  hydrochloric 
acid,  and  the  oxides  of  nitrogen,  lead,  iron  and  arsenic,  are  accord- 
ing to  the  methods  of  Krauch. 

(# )  Sulphurous  acid.  To  a  weak  yellow  solution  of  iodine,  previ- 
ously treated  with  starch  paste,  the  diluted  sulphuric  acid  is  added. 
In  presence  of  sulphurous  acid  decolorization  takes  place.  Or  the 
sulphurous  acid  is  reduced  with  zinc  or  aluminium  to  hydrogen  sul- 
phide, and  the  latter  detected  by  means  of  lead-paper  or  an  alkaline 
solution  of  sodium  nitroprusside  (very  delicate). 

(<£)  Hydrochloric  acid.  Two  grams  sulphuric  acid  are  diluted 
to  30  c.c.  and  a  few  drops  of  a  silver  nitrate  solution  are  added. 
Presence  of  hydrochloric  acid  is  indicated  by  turbidity. 

(<r)  Oxides  of  nitrogen.  A  very  trustworthy  test  is  the  diphenyl- 
amine  test.  This  is  conducted,  according  to  Wagner,  in  the  fol- 
lowing manner  :  To  i  c.c.  pure  distilled  water  in  a  porcelain  cap- 
sule, a  few  crystals  of  diphenylamine  are  added,  followed  succes- 
sively by  two  additions,  ^  c.c.  each,  of  the  cone,  acid  under 
examination.  Traces  of  nitric  acid  produce  a  blue  coloration  after 
a  time.  (The  same  reaction  is  shown  by  other  oxidizing  sub- 
stances. ) 

(dQ  Lead.  The  acid  is  mixed  with  5  times  the  volume  of 
strong  alcohol.  A  turbidity  after  a  time  indicates  the  presence  of 
lead  sulphate,  which  is  further  identified  by  dissolving  the  precipi- 
tate in  ammonium  acetate,  and  testing  with  potassium  chromate  or 
hydrogen  sulphide. 

(<?)  Iron.  The  acid  is  boiled  with  a  few  drops  of  nitric  acid 
diluted  with  a  little  water.  It  is  allowed  to  cool,  and  ammonium 
sulpho-cyanide  is  added.  A  red  tint  indicates  the  presence  of  iron. 

(/)  Arsenic.  Two  grs.  cone,  sulphuric  acid,  diluted  with  an 
equal  volume  of  water,  are  warmed  with  a  few  pieces  of  granu- 


SULPHURIC    ACID    AND    ANHYDRIDE.  5 

lated  zinc  until  strong  evolution  of  gas  begins.  A  yellow  coloration 
indicates  arsenic.  Sulphuric  acid  may  contain  as  high  as  o.  i  per 
cent.,  and  in  exceptional  cases  as  high  as  0.4  per  cent,  arsenic.  On 
account  of  the  injurious  action  of  the  latter,  a  quantitative  estima- 
tion is  often  desirable.  For  this  purpose  the  following  method  of 
Lunge  is  recommended : 

About  20  grams  acid  are  diluted  with  an  equal  volume  of  water. 
In  order  to  reduce  the  arsenic  acid  present,  sulphurous  acid  is  con- 
ducted into  the  liquid  for  some  time,  until  the  odor  is  pronounced. 
Heat  is  applied  and  carbonic  acid  is  conducted  in  until  the  odor  dis- 
appears, when  carbonate  of  soda  is  added  to  exact  neutralization, 
followed  by  a  small  quantity  of  bicarbonate  of  soda.  The  liquid  is 
then  titrated  with  TV  normal  iodine  solution,  using  starch  solu- 
tion as  indicator,  (i  c.c.  iodine  solution  —  0.00495  gr.  As.2O3. ) 
Any  appreciable  quantity  of  iron  must  previously  be  removed. 

Fuming  Sulphuric  Acid  and  Anhydride. 

Lately  there  has  appeared  in  commerce  fuming  sulphuric  acid  in 
form  of  an  oily,  thick  liquid  containing  a  high  percentage  of  SO, 
(upward  of  70  per  cent.),  or  in  form  of  a  solid,  which  is  used  prin- 
cipally in  the  dye  industry.  Anhydride  is  a  solid  mass  containing 
80-90  per  cent,  free  SOS  and  10-20  per  cent,  monohydrate.  The 
analysis  is  confined  principally  to  the  estimation  of  anhydride  and 
sulphurous  acid.  In  weighing  the  substance  and  subsequently  dilut- 
ing, special  care  is  to  be  observed  in  preventing  on  the  one  hand 
the  absorption  of  moisture  while  weighing,  and  on  the  other  hand 
in  preventing  the  volatilization  of  anhydride  and  sulphurous 
acid  by  the  heat  produced  in  diluting.  The  following  procedure 
recommended  by  Lunge  has  been  found  most  advantageous : 

The  substance  is  weighed  in  a  thin  bulb  tube,  both  ends  of  which 
are  drawn  out  to  capillaries.  The  weight  of  the  empty  bulb  is  first 
ascertained.  3-5  grams  of  the  substance,  carefully  melted,  if  neces- 
sary, in  a  sand-bath  or  iron  plate,  are  drawn  into  the  bulb.  To 
effect  this  a  flask  with  a  narrow  neck  and  a  caoutchouc  stopper  with 
single  perforation  is  used.  Through  the  stopper  a  tight-fitting  glass 
tube  with  stopcock  issues,  over  the  end  of  which  a  rubber  tube  is 
drawn.  On  applying  suction  with  the  mouth  to  this,  and  then 
quickly  closing  the  stopcock,  a  partial  vacuum  is  produced.  The 


6  CHEMICAL-TECHNICAL    ANALYSIS. 

open  end  of  the  rubber  tube  is  drawn  over  the  capillary  on  the 
bulb,  the  other  end  of  which  is  introduced  into  the  liquid  to  be 
analyzed.  By  opening  the  cock  the  necessary  amount,  which,  how- 
ever, should  not  more  than  half  fill  the  bulb,  is  introduced.  The 
capillary  is  then  drawn  from  the  liquid,  cleaned,  sealed,  and 
weighed  in  horizontal  position.  The  bulb  is  now  placed  open  end 
downward  in  a  small  Erlenmeyer  flask,  whose  mouth  is  closed  by 
the  bulb,  and  which  contains  sufficient  water  to  deeply  immerse  the 
capillary.  The  sealed  end  is  broken,  the  liquid  is  allowed  to  run 
out,  and  the  bulb  is  washed  first  by  washing  through  the  capillary 
and  eventually  by  drawing  water  into  the  entire  bulb.  When  the 
most  concentrated  oil  (about  70  per  cent. )  is  used,  direct  addition 
to  water  without  loss  cannot  be  accomplished.  In  this  case  both 
ends  of  the  bulb,  prepared  as  above,  are  sealed,  and  the  bulb  is  in- 
troduced into  a  well-ground  glass-stoppered  flask,  containing  con- 
siderable water.  The  flask  is  shaken  to  break  the  bulb,  and  after- 
wards allowed  to  stand.  The  contents  of  the  flask  are  poured  into 
a  graduated  flask,  diluted  to  500  c.c.  exactly,  and  in  one  portion 
the  total  acid  is  estimated  by  alkali,  while  in  another  the  sulphurous 
acid  is  titrated  with  iodine  solution.*  In  the  calculation,  the  result 
of  the  titration  with  caustic  soda  is  expressed  in  per  cent,  sulphuric 
anhydride  (a),  and  that  of  titration  with  iodine  solution  in  per  cent, 
sulphurous  anhydride  (b).  The  value  of  (b)  is  transformed  into 
sulphuric  anhydride,  and  the  value  (c)  so  obtained  subtracted  from 
a ;  the  difference  (a— c)  then  represents  the  total  amount  of  sul- 
phuric anhydride.  Moreover,  if  the  sum  (a-c)  +  b  be  subtracted 
from  100,  the  quantity  of  water  of  hydration  can  be  ascertained, 
and  the  monohydrate  present  can  be  calculated  in  percentage  (d). 
The  difference  100 — (d  +  b)  yields  the  percentage  of  free  active 
anhydride. 

Example. — In  the  examination  of  a  sample  of  fuming  sulphuric 
acid  ther  esult  of  the  titration  with  alkali  showed  85.5  percent. 
SO3  (a),  the  titration  with  iodine  0.6  per  cent.  SO2  (b).  The 
value  b  is  changed  to  SO3  by  the  proportion  64  :  80=0.6  :  c,  and 
from  this  c  is  found  to  equal  0.75  per  cent.  The  difference  a-c= 
84.75  Per  cent-  SO3.  The  sum  (a-c) 4^=85.3 5  per  cent.,  which 

*  In  weighing,  the  stopcock  bulb  pipettes  of  Lunge  and  Rey  may  also  be  used 
to  advantage. 


NITROSO    ACID.  7 

subtracted  from  100  gives  14.65  per  cent,  water  of  hydration. 
This,  according  to  the  proportion  18  :  981=14.65  :  d,  corresponds 
to  d— 79.76  per  cent,  monohydrate.  There  remains,  therefore, 
100 — (d  +  b)=ioo— 80.36=19.64  per  cent,  sulphuric  anhydride. 

The  acid  contains,  therefore,  79.76  percent.  H2SO4. 

19.64  "  SO3. 

0.60  "  SO2. 

If  the  fuming  sulphuric  acid  contains  no  sulphurous  acid,  the 
difference  roo-a  yields  the  percentage  of  water  of  hydration.  The 
quantity  of  monohydrate  corresponding  to  this  value  is  obtained  from 
the  proportion  18  :  98  :  :  (loo-a)  :  d,  and  from  the  difference 
100 — d  the  amount  of  free  anhydride  is  found. 

Nitroso  Acid  (Nitrated  Acid). 

The  proportion  of  total  compounds  of  nitrogen  in  nitroso  acid,  a 
question  of  great  importance  in  the  lead-chamber  process,  is  esti- 
mated by  means  of  the  Lunge  nitrometer.  The  estimation  depends 
on  the  fact  that  the  acids  containing  nitrogen,  which  are  dissolved 
in  the  sulphuric  acid,  are  reduced  by  contact  with  metallic  mercury 
to  NO,  the  amount  of  which  is  determined.  The  nitrometer  in  its 
original  form  presents  the  following  arrangement :  The  tube  (a) 
(Figure  i),  divided  in  ^  or  -^  c.cm.,  is  provided  with  a  cup 
above  and  has  a  capacity  upward  of  50  c.c.  Directly  below  the 
cup  is  a  three-way  cock,  whose  straight  opening  establishes  commu- 
nication with  the  eudiometer,  while  a  second  indirect  opening  allows 
the  contents  of  the  cup  to  empty  through  the  axis  of  the  stopcock. 
For  this  purpose  a  rubber  tube,  provided  with  a  screw  clamp  and  a 
glass  tube,  is  fastened  to  the  stopcock.  Finally,  the  cock  can  be 
placed  so  that  the  cup  communicates  with  neither  opening. 

The  tube  (£)  is  made  of  strong  glass  tubing  of  nearly  the  same 
diameter  and  capacity  as  (0).  Both  tubes  are  attached  to  a  stout 
rubber  tube.  The  remainder  is  self-evident.  During  manipula- 
tion the  tube  (£)  is  so  adjusted  that  the  lower  end  is  somewhat 
above  the  stopcock  of  (0),  which  is  then  opened  ;  mercury  is 
poured  into  (£)  until  the  level  enters  the  cup.  Since  the  mercury 
enters  (#)  from  below,  no  air-bubbles  collect  on  the  glass  walls. 
The  cock  is  closed,  the  mercury  run  out  of  the  cup  through  the  side- 


CHEMICAL-TECHNICAL    ANALYSIS. 


opening,  the  tube  (^)  is  lowered,  and  the  cock  is  adjusted  to  cut 
off  all  communication. 

The  nitroso  acids  are  now  run  into  the  cup  from  a  very  small 
pipette  (the  stronger  acids  require  0.5  c.c.,  the  weaker  2-5  c.c.), 
and  the  level  in  the  tube  (<£)  is  lowered  somewhat.  The  cock  is 
opened,  and  the  acid  is  allowed  to  drain  into  tube  (#),  care  being 
taken  to  admit  no  air.  The  cup  is  then  rinsed  in  the  same  manner 
twice,  first  with  2-3  c.c.,  and  again  with  1—2  c.c.  absolutely  nitroso 
free,  concentrated  sulphuric  acid.  The  entire  volume  of  acid  intro- 
duced should  not  exceed  8-10 
c.c.  Gas  evolution  is  started  by 
removing  the  tube  (0)  from  its 
clamp,  placing  it  in  an  almost 
horizontal  position  and  suddenly 
righting  a  number  of  times  to 
insure  thorough  mixture  of  acid 
and  mercury.  It  is  then  shaken 
for  1-2  minutes  until  gas  evolu- 
tion ceases.  Usually  this  time 
suffices.  It  is  allowed  to  stand 
until  the  acid  clears,  cools  off, 
and  the  foam  disappears,  an 
operation  which  lasts  but  a  short 
time.  The  tube  (£)  is  raised 
to  bring  the  mercury  level  suffi- 
ciently above  that  in  (a)  to  cor- 
respond to  the  volume  of  sul- 
phuric acid  in  the  latter  (for 
every  7  mm.  acid  i  mm.  mercury),  after  which  the  volume  of 
nitric  oxide,  which  should  never  exceed  50  c.c.,  is  read  off,  reduced 
to  o°  C.  and  760  mm.  pressure.  The  calculation  of  the  amount  of 
nitrous  oxide  is  simple,  since  every  c.c.  reduced  volume  equals 
1.701  mg.  N2O3.  Any  nitric  acid  present  is  thereby  also  reckoned 
as  N,OS. 

Lunge  has  prepared  tables  by  means  of  which  the  reduced 
volume,  as  well  as  the  amount  of  nitroso  acid,  may  be  read  off 
directly.  If  it  should  be  found  desirable,  after  reading,  to  ascertain 
whether  the  acid  column  in  the  eudiometer  is  compensated  for  by  the 


FIG.  i. — Lunge's  Nitrometer. 


NITROSO    ACID. 


9 


mercury  column  in  (£),  the  stopcock  is  opened.  Should  the  level 
of  the  acid  rise,  the  pressure  was  too  great.  Should  it  fall,  however, 
the  pressure  was  insufficient.  Hence  the  volume  read  was  in  the 
first  instance  too  small,  in  the  second  instance  too  large.  Given, 
for  example,  15.3  c.c.,  should  the  acid  rise  to  15.2  on  opening  the 
stopcock,  the  corrected  volume  would  equal  15. 3  +  0. 1=15. 4  c.c. 

The  apparatus  is  prepared  for  a  new  determination  by  opening 
the  cock  and  raising  the  tube  (^),  thereby  forcing  out  the  nitric  oxide 
which  enters  the  cup,  followed  by  the  acid  containing  suspended 
mercurous  sulphate.  The  moment 
mercury  enters  the  cup  the  stop- 
cock is  closed  and  the  acid  is  al- 
lowed to  issue  through  the  axial 
perforation.  The  final  traces  are 
removed  from  the  cup  with  filter- 
paper,  after  which  the  stopcock  is 
re -arranged  to  prevent  communica- 
tion either  way. 

Should  a  nitroso  acid  contain  an 
appreciable  quantity  of  sulphurous 
acid,  it  is  necessary  to  add  to  the 
same  in  the  cup  a  quantity  of  potas- 
sium permanganate. 

The  new  gasvolumeter  of  Lunge 
is  preferable  to  the  original  nitrome- 
ter. It  differs  from  the  latter  prin- 
cipally in  that  the  decomposition 
of  the  nitroso  acids  and  the  meas- 
urement of  the  gas  volume  formed  do  not  take  place  in  the  same 
tube,  but  in  separate  parts  of  the  apparatus.  Further,  temperature 
and  pressure  readings,  as  well  as  the  involved  calculations,  are 
eliminated  in  reading  the  gas  volume,  and  finally  the  apparatus  is 
useful  in  a  number  of  other  analytical  operations. 

As  seen  in  the  accompanying  illustration  (Fig.  2),  the  one  part 
of  the  apparatus — the  reaction  vessel,  consisting  of  tubes  (.£)  and 
(Z>),  the  stopcock  (/)  and  the  cup  (//) — is  very  similar  to  that  of 
the  original  nitrometer.  It  differs  therefrom,  however,  in  that  the 
tube  (/?),  used  for  decomposing  the  acid,  is  not  graduated,  and  the 


FIG.  2. — Lunge's  Gasvolumeter. 


10  CHEMICAL-TECHNICAL    ANALYSIS. 

stopcock  possesses,  instead  of  an  axial  perforation,  a  second  side- 
perforation,  which  establishes  communication  between  the  small 
tube  (V)  and  the  tube  (Z>).  In  this  part  of  the  apparatus  the 
decomposition  of  the  acid  is  carried  out  exactly  as  before.  The 
second  part  of  the  apparatus  consists  of  three  tubes  (4),  (-#),  and 
(C),  which  are  connected  with  each  other  by  means  of  a  three- 
way  tube.  (A~)  is  a  glass  measuring  tube  of  50  c.c.  capacity, 
graduated  in  ^  c.c.  and  provided  with  the  double-bored  stopcock 
Qf),  which  establishes  communication  of  (A}  with  the  straight 
tube  (/£),  as  well  as  with  the  rectangular  tube  (*).  (£)  serves 
as  a  reduction  tube.  Under  the  wide  portion,  which  has  a 
capacity  of  100  c.c.,  the  tube,  to  the  extent  100  c.c.  to  125 
c.c.,  is  divided  in  ^  c.c.,  and  is  filled  exactly  with  so  much  air 
that  the  volume  of  the  latter  at  o°  and  760  mm.  when  dry  amounts 
to  100  c.c.  The  volume  V,  which  represents  the  space  which 
100  c.c.  air  at  o°  and  760  mm.  pressure  would  occupy  at  the  observed 
temperature  t  and  the  pressure  b,  is  found  by  the  following  equa- 

tion: V=  —       v   73~r  ;    —  ;  —  ^     One  drop  of  cone,  sulphuric  acid 


is  now  introduced  into  (£}  ;  mercury  is  poured  in  the  tube  (  C  )  until 
the  mark  in  (J?),  representing  the  volume  F,  is  reached,  when  it  is 
closed  by  either  carefully  sealing  the  latter,  care  being  taken  not  to 
warm  (j9),  or  by  closing  a  previously  attached  tight-fitting  stopcock. 
The  decomposition  of  the  nitroso  acid  is  then  carried  out  in  the 
reaction  tube  as  previously  described,  and  after  (A)  has  been  filled 
completely  with  mercury  to  the  end  of  the  small  tube  (/),  by 
raising  (C),  the  tubes  (^)  and  (A)  are  placed  side  by  side  and 
(  C  )  is  connected  by  means  of  a  rubber  tube  with  (<?)  in  such  a 
manner  that  the  two  touch  each  other  glass  to  glass  without  enclos- 
ing air  between  them.  {E}  is  then  raised,  (C)  is  lowered,  the 
stopcocks  (/)  and  (g)  are  opened,  and  at  the  moment  that  the 
pressure  has  driven  all  the  gas  over  into  (A)  and  the  acid  issues 
from  (Z>)  through  (V)  and  (/)  to  the  stopcock  (#•),  the  latter  is 
closed,  together  with  (/),  and  (JD}  and  (A)  are  disconnected.  (C) 
is  now  raised  until  the  mercury  in  (J?)  rests  at  precisely  100.  By 


*  In  very  exact  determinations,  I  mm.  is  subtracted  for  values  of  /  up  to  12°  ; 
2  mm.  for  values  from  13-19°,  and  3  mm.  for  values  from  20-25°,  to  aU°w  for  ex- 
pansion of  the  mercury. 


BRINE.  11 


means  of  a  double  clamp-holder  (C)  and  (^5)  are  moved  up  or 
down  in  concert  until  the  mercury  in  (^4)  and  (jff)  reaches  the 
same  level,  but  simultaneously,  however,  remains  at  100  in  (^9). 
Since  the  gas  in  (.#)  is  so  far  compressed  as  to  occupy  the  same 
volume  as  at  o°  and  760  mm.  pressure,  the  readings  in  (A)  repre- 
sent the  gas  reduced  to  the  same  normal  condition.  The  tempera- 
ture in  (A")  and  (^)  is  supposed  to  be  the  same,  a  condition  quickly 
produced  by  the  mercury.  Ten  minutes  are  required  before 
the  final  adjustment  of  the  apparatus,  when  large  quantities  of 
nitric  oxide  are  used.  By  the  use  of  these  particular  reaction  tubes, 
the  inconveniences  of  foam  and  slime  and  the  compensation  for  an 
acid  column  are  avoided.  The  eudiometer  remains  clean,  in  conse- 
quence of  which  a  large  number  of  determinations  can  be  under- 
taken without  constant  cleaning. 

6.  Brine. 

The  following  determinations  are  usually  carried  out  : 

Specific  gravity,  total  chlorine,  sulphuric  acid,  ferric  oxide, 
alumina,  lime,  magnesia,  and  carbonic  acid.  In  addition,  qual- 
itative tests  for  potassium,  bromine  and  iodine  are  made,  and  some- 
times these  constituents  are  determined  quantitatively. 

(a)  Specific  gravity.  This  is  determined  by  means  of  the 
pyknometer  in  the  usual  manner. 

(£)  Total  chlorine.  10  c.c.  brine  are  diluted  to  1000  c.c.  A 
gravimetric  or  volumetric  determination  of  chlorine  in  25  c.c.  is 
made. 

(c)  Sulphuric  acid.  To  50  c.c.  brine  a  few  drops  of  hydrochloric 
acid  are  added.  (Sodium  chloride  is  precipitated  in  this  instance 
from  the  very  concentrated  brine  solution.)  One  to  two  volumes 
of  water  are  added,  and  the  hot  solution  is  precipitated  with  barium 
chloride. 

(//)  Ferric  oxide  and  alumina.  250  c.c.  brine,  previously  heated 
with  a  small  quantity  of  nitric  acid,  are  precipitated  after  addition 
of  ammonium  chloride  with  ammonia.  The  precipitate,  of  which 
there  is  usually  a  small  quantity,  is  filtered,  and  both  constituents 
are  weighed  together.  The  presence  of  iron  can  be  ascertained 
previously  in  a  separate  portion  of  the  brine,  oxidized  with  nitric 
acid,  by  the  addition  of  ammonium  sulpho-cyanide. 


12  CHEMICAL-TECHNICAL    ANALYSIS. 

(«?)  Lime  is  precipitated  with  ammonium  oxalate  in  the  filtrate 
from  d.  The  precipitate  is  treated  in  the  usual  manner. 

(/)  Magnesia.  To  the  filtrate  from  the  lime  sodium  hydrogen 
phosphate  is  added.  The  precipitate  which  forms  is  weighed  as 
magnesium  pyrophosphate. 

(£•)  Carbonic  acid.  1-2  drops  methyl-orange  are  added  to  ^ 
liter  brine.  The  solution  is  then  titrated  with  ^  normal  hydro- 
chloric acid  to  red  coloration.  (2HC1  =  iCO2.) 

(Ji)  Potassium,  bromine  and  iodine.  The  qualitative  tests  for 
these  three  bodies  can  be  carried  out  in  the  following  manner : 

A  large  quantity  of  the  brine  is  evaporated  to  y$  its  original  vol- 
ume. Any  salt  which  separates  is  filtered  off  or  thoroughly  drained. 
The  filtrate  is  again  evaporated,  and  any  salt  which  separates  is 
removed  as  before.  The  mother-liquor  is  then  divided  into  two 
portions.  In  the  one,  by  means  of  platinic  chloride,  a  test  is  made 
for  potassium,  which  is  precipitated  in  form  of  yellow  crystalline 
potassium -platinic  chloride.  To  the  other  solution,  which  must  be 
frequently  agitated,  chloroform  and  chlorine-water,  drop  by  drop, 
are  added.  Iodine  will  first  be  precipitated — a  fact  readily  noticed 
by  the  violet  color  of  the  chloroform.  Later,  bromine  is  recog- 
nized by  the  lemon  or  yellow  color  imparted  to  the  chloroform 
layer. 

The  quantitative  estimation  of  these  three  bodies  will  not  be 
described  here. 

The  results  found  are  arranged  according  to  the  same  principles 
which  will  be  considered  later  under  the  determination  of  the  more 
exact  composition  of  boiler-water. 

7.  Crude  Hydrochloric  Acid. 

This  substance  may  contain  as  impurities  :  sulphuric  acid,  sul- 
phurous acid,  chlorine,  arsenic  and  iron  compounds,  alumina,  lime, 
alkali  metals,  hydrobromic  acid  and  hydriodic  acid. 

The  chlorine  is  usually  to  be  attributed  to  the  presence  of  nitrous 
acid  in  the  sulphuric  acid.  Arsenic  and  iron  compounds  arise  from 
the  crude  sulphuric  acid.  Qualitative  tests  for  these  various  impu- 
rities are  made  by  the  usual  method.  (See  also  Sulphuric  Acid.) 

For  the  qualitative  estimation  of  arsenic  Krauch  recommends  the 
following  procedure:  To  i.o  gr.  hydrochloric  acid,  diluted  with  10 


SODA.  13 

c.c.  water,  5  c.c.  freshly -prepared  hydrogen  sulphide  water  are  care- 
fully added,  so  as  to  form  a  supernatant  layer.  In  the  absence  of 
arsenic  no  coloration  and  no  yellow  ring  should  form  between  the 
two  liquids  when  warm  or  cold. 

Of  the  quantitative  determinations  particular  attention  is  called  to 
those  of  arsenic,  iron  and  sulphurous  acid. 

(a)  Arsenic.  In  order  to  reduce  any  arsenic  acid  present,  sul- 
phurous acid  is  conducted  into  the  solution  for  a  protracted  period. 
The  latter,  after  expulsion  of  the  sulphurous  acid,  is  saturated  with 
hydrogen  sulphide,  when  arsenic  is  precipitated  as  trisulphide.  The 
precipitate  is  filtered,  thoroughly  washed,  dissolved  from  the  filter 
with  ammonia,  and  evaporated  in  a  weighed  glass  or  porcelain  dish, 
after  which  the  trisulphide  remaining  is  dried  at  100°  and  weighed. 

(£)  Iron.  A  measured  quantity  of  the  acid  is  treated  with  zinc, 
free  from  iron,  in  a  current  of  carbonic  acid,  in  order  to  reduce  all 
the  iron  present.  To  the  copiously  diluted  acid  a  20  per  cent, 
solution  of  manganous  chloride  or  sulphate  is  then  added,  and  the 
liquid  is  titrated  with  an  accurately  standardized,  about  ^  normal, 
potassium  permanganate  solution. 

(c)  Sulphurous  acid.  This  is  oxidized  with  permanganate, 
iodine  or  hydrogen  peroxide  to  sulphuric  acid,  and  precipitated  with 
barium  chloride.  Sulphuric  acid  originally  present  must  likewise 
be  estimated  and  subtracted  from  the  above. 

8.  Soda. 

At  present  soda  is  derived  principally  from  two  well-known  pro- 
cesses— the  Le  Blanc  and  the  ammonia  soda  process.  That  from  the 
former  may  contain,  as  chief  impurities :  sodium  sulphate,  sodium 
chloride,  sodium  silicate,  sodium  aluminate,  sodium  hydrate,  sodium 
sulphide,  sodium  sulphite,  ferric  oxide,  calcium  carbonate,  silica 
and  carbon.  Ammonia  soda  is  mostly  very  pure,  and  contains  as  a 
rule  only  sodium  chloride  (^  to  about  2^  percent.),  at  times 
sodium  bicarbonate,  and  at  the  most  only  traces  of  sodium  hydrate. 
At  the  same  time  it  must  be  admitted  that  at  present  the  Le  Blanc 
soda  comes  into  commerce  in  a  very  pure  state  on  account  of  the 
general  demand  for  soda  containing  not  more  than  0.4  per  cent, 
matter  insoluble  in  water,  o.i  per  cent,  matter  insoluble  in  hydro- 
chloric acid,  and  about  0.02  percent,  ferric  oxide. 


14  CHEMICAL-TECHNICAL    ANALYSIS. 

Following  are  the  methods  of  investigation  for  technical  soda 
selected  with  regard  to  its  possible  impurities.  It  is  hardly  neces- 
sary to  state  that  the  simultaneous  presence  of  many  of  the  impuri- 
ties cited,  such  as  hydrate  and  bicarbonate  of  soda,  for  instance,  is 
excluded.  It  is  an  advantage  to  find  out  qualitatively  the  presence 
of  individual  constituents  such  as  sodium  hydrate,  sodium  sulphide, 
and  sodium  sulphite. 

The  qualitative  examination  for  sodium  hydrate  is  similar  to  the 
quantitative.  The  soda  solution  is  precipitated  with  an  excess  of 
barium  chloride,  and  the  filtrate  is  tested  for  alkali  by  means  of 
litmus  or  phenol-phthalein.  The  presence  of  sulphide  of  soda  is 
determined  by  means  of  an  alkaline  solution  of  sodium  nitroprus- 
side  or  lead-paper.  To  test  for  sodium  sulphite  a  sample  is  acidified 
with  acetic  acid,  starch  paste  is  added,  and  notice  is  taken  whether 
a  slowly-added  dilute  iodine  solution  is  decolorized. 

Quantitative  Examination. 

53  grs.  soda  (corresponding  to  one-half  the  molecular  weight)  are 
first  dissolved  in  warm  water  in  a  large  beaker  glass,  allowed  to 
stand  for  ^  hour,  and  then  filtered  through  a  dried  and  weighed 
filter  into  a  liter  flask.  After  washing  the  filter  the  flask  is  filled  to 
the  mark.  The  residue  is  dried  at  100°  to  constant  weight,  which 
represents  the  matter  "  insoluble  in  water."  Should  a  more  thor- 
ough examination  of  this  be  necessary,  the  filter  is  again  moistened 
with  water  and  lixiviated  with  hot  dilute  hydrochloric  acid.  Ferric 
oxide,  alumina,  calcium  carbonate  and  magnesium  carbonate  are 
dissolved.  If  the  filter  now  be  washed,  dried  and  weighed,  it  will 
contain  the  silica  and  carbon.  By  ignition  of  the  filter  the  carbon 
is  burned  off,  and  the  ash  which  is  weighed  consists  only  of  silica. 
In  the  acid  filtrate  iron  only  is  usually  quantitatively  estimated.  To 
accomplish  this  ammonia  is  added,  and  the  resulting  ferric  hydrate 
is  dissolved  in  i  :  4  sulphuric  acid,  reduced  with  zinc  and  titrated 
with  permanganate.  The  remainder  of  the  insoluble  matter,  after 
deducting  ferric  oxide,  silica  and  carbon,  may  be  considered  as  cal- 
cium carbonate. 

Examination  of  the  Aqueous  Solution. 

(a)  Total  active  soda  (with  acid).  50  c.c.  solution,  representing 
2.65  grs.  soda,  are  titrated  with  hydrochloric  acid  (preferably  ^ 


SODA.  15 

normal),  with  addition  of  methyl -orange,  and  the  result  is  calculated 
as  sodium  carbonate.  This  includes  as  sodium  carbonate  sodium 
hydrate,  sodium  sulphide,  sodium  sulphite,  sodium  silicate,  sodium 
aluminate,  and  finally  sodium  bicarbonate. 

(<£)  Sodium  sulphate.  50-100  c.c.  solution  are  acidified  slightly 
with  hydrochloric  acid,  and  the  hot  solution  is  precipitated  with 
barium  chloride. 

(<r)  Sodium  chloride.  20-50  c.c.  solution  are  acidified  with 
nitric  acid  and  precipitated  with  silver  nitrate.  The  presence  of 
considerable  quantities  of  sodium  sulphide  will  influence  the  accu- 
racy. 

(X)  Sodium  hydrate.  100  c.c.  soda  solution  are  mixed  in  a  large 
beaker  with  a  few  drops  of  phenol-phthalein  and  150  c.c.  of  a  10  per 
cent,  barium  chloride  solution.  The  solution  is  copiously  diluted 
and  titrated  with  Tnth  normal  oxalic  acid.  Previous  filtration  is 
unnecessary. 

(<?)  Sodium  sulphide.  TOO  c.c.  solution  are  brought  to  boiling, 
and  after  the  addition  of  ammonia  an  ammoniacal  silver  solution  is 
added  drop  by  drop  until  no  further  precipitation  of  silver  sulphide 
ensues.  In  order  to  aid  this  observation  the  solution  is  filtered  near 
the  end  of  the  operation,  and  the  filtrate  is  titrated  further.  This 
is  repeated  until  only  a  slight  turbidity  appears  in  the  filtrate.  To 
prepare  the  ammoniacal  silver  solution  13.845  grs.  pure  silver  are 
dissolved  in  pure  nitric  acid,  250  c.c.  ammonia  are  added  to  the 
solution,  and  the  whole  is  diluted  to  one  liter.  Every  c.c.  of  this 
solution  represents  0.005  ST-  Na.^S. 

(/)  Sodium  sulphite.  100  c.c.  soda  solution  are  acidified  with 
acetic  acid,  starch  paste  is  added,  and  the  solution  is  titrated  with 
Tfrth  normal  iodine  solution  until  the  blue  coloration  appears.  2 
atoms  iodine  represent  i  molecule  sodium  sulphite,  or  i  c.c.  iodine 
solution  =  0.0063  gr.  Na.,SO3.  The  sodium  sulphide  found  in  (i) 
calculated  into  sodium  sulphite  must  be  subtracted  from  this  re- 
sult. 

(g)  Sodium  silicate  and  sodium  aluminate.  100  c.c.  solution  are 
acidified  in  a  spacious  porcelain  dish  with  hydrochloric  acid  and 
evaporated  to  dryness.  The  silica  is  separated  as  usual,  and  in  the 
filtrate  the  alumina  is  determined  by  precipitation  with  ammonia. 

(^)  Bicarbonate.     The   estimation    depends    on   the    fact    that 


16  CHEMICAL-TECHNICAL    ANALYSIS. 

bicarbonate  is  changed  to  normal  carbonate  by  the  addition  of 
caustic  soda.  If,  therefore,  an  excess  of  titrated  caustic  soda  be 
added  to  the  soda  solution,  the  carbonate  be  precipitated  with 
barium  chloride,  and  the  excess  of  sodium  hydrate  be  titrated,  then 
the  amount  of  hydrate  used  represents  the  quantity  of  bicarbonate 
present  ;  in  fact,  i  molecule  sodium  hydrate  is  equivalent  to  i  mole- 
cule bicarbonate  according  to  the  equation 


Na  H  CO3+Na  OH=Na2  CO3+H2O. 

To  conduct  this,  a  separate  portion  of  the  soda  (about  5  grs.)  is 
weighed  and  dissolved  in  a  beaker  of  about  i  liter  capacity,  with 
100  c.c.  water  which  has  been  previously  boiled  and  cooled  to  15- 
20°.  Agitation  and  warming  the  solution  are  to  be  avoided,  since 
the  bicarbonate  will  lose  carbonic  acid  thereby;  on  the  other 
hand,  by  crushing  the  soda  in  the  vessel  solution  may  be  acceler- 
ated. 25  c.c.  y?,  normal  sodium  hydrate  solution  are  now  added, 
followed  by  150  c.c.  10  per  cent,  barium  chloride  and  a  few  drops 
of  phenol  -phthalein.  About  500  c.c.  distilled  water  are  added, 
and  the  excess  of  alkali  is  titrated  with  ^  normal  oxalic  acid. 

Since  sodium  hydrate  usually  contains  carbonate,  25  c.c.  are 
simultaneously  diluted  with  100  c.c.  water,  150  c.c.  barium 
chloride,  and  a  few  drops  of  phenol  phthalein  are  added,  and  the 
solution  titrated  with  ^  normal  oxalic  acid.  Should  24.75  c-c- 
oxalic  acid  (instead  of  25)  be  required,  they  will  represent  the 
actual  amount  of  caustic  soda  in  the  solution. 

Calculation.  —  If  5  grs.  soda  were  taken,  and  in  titrating  13.5 
c.c.  ^  normal  oxalic  acid  were  used,  then  24.75  —  I3-5rr:I1-25 
c.c.  y?,  normal  oxalic  acid,  required  by  the  bicarbonate.  These 
correspond  to  0.02  X  11.25  —  0.  225  gr.  caustic  soda.  According 
to  the  proportion  4o(NaOH)  :  84(NaHCO3)  =  0.225  :  x,  x  — 
0.4725  gr.  NaHCO3  or  9.45  per  cent,  bicarbonate. 

(*')  Moisture.  This  important  determination  is  conducted  by 
heating  about  2  grs.  soda  in  a  platinum  crucible  at  a  low  heat,  and 
determining  the  consequent  loss  in  weight.  Any  bicarbonate  pres- 
ent is  thereby  decomposed.  In  the  same  manner  silica  will  expel 
an  equivalent  quantity  of  carbonic  acid.  On  account  of  the  com- 
paratively small  error  produced,  simple  desiccation  over  concen- 
trated sulphuric  acid  is  also  recommended. 


SODIUM    ALUMINATE.  17 

Freshly -prepared  soda  should  not  contain  more  than  J^-^  per 
cent,  moisture.  Even  well-preserved  soda,  after  some  time,  should 
not  contain  much  over  i  per  cent.  Stored  in  moist  air,  however, 
the  quantity  of  moisture  can  rise  to  10  per  cent. 

Arrangement  of  the  Analytical  Results. 

When  the  insoluble  constituents  are  determined  only  to  the  extent 
mentioned,  the  calculation  is  very  simple.  The  amounts  of  soda 
corresponding  to  caustic  soda,  sodium  sulphide,  sodium  sulphite, 
sodium  bicarbonate — furthermore,  sodium  silicate  (Na2SiO3)  and 
sodium  aluminate  (Na2Al.2O4) — are  calculated  into  sodium  carbonate, 
and  the  sum  of  these  is  subtracted  from  the  results  obtained  under 
(a).  In  this  manner  the  true  amount  of  sodium  carbonate  is  ob- 
tained. This  could  also  be  done  by  a  direct  estimation  of  the 
carbonic  acid  and  subsequent  calculation  into  carbonate  of  soda — a 
process  often  preferred.  The  strength  of  a  soda  is  expressed  in 
degrees.  German  degrees  represent  the  strength  expressed  as  car- 
bonate of  soda ;  French,  or  Gay-Lussac,  as  oxjde  of  sodium.  Des- 
croizilles  degrees  show  how  many  parts  by  weight  of  sulphuric  acid 
(H.,SO4)  are  neutralized  by  100  parts  soda.  These  degrees  bear  the 
following  relation  to  one  another:  53.04  German  degrees  equal 
31.04  Gay-Lussac  or  49  Descroizilles  degrees. 

9.  Sodium  Aluminate. 

This  contains,  besides  its  two  constituents,  small  quantities  of 
matter  insoluble  in  water,  silica  and  traces  of  iron,  which  are  deter- 
mined in  the  usual  manner. 

The  estimation  of  soda  and  alumina  is  carried  out  volumetrically 
by  the  method  of  Lunge.  The  method  is  based  on  the  following 
process  :  If  to  a  solution  of  sodium  aluminate  hydrochloric  acid  be 
added,  the  soda  is  neutralized  and  alumina  begins  to  separate. 
This  is  explained  by  the  following  reaction  : 

Na.2OAl203  +  2HC1  +  2H2O  =  2NaCl  +  A12(OH)6. 

Were  phenol -phthalein  present,  the  color  would  disappear  as  soon 
as  the  soda  was  neutralized.  The  quantity  of  acid  used,  therefore, 
is  a  fneasure  for  the  amount  of  soda  present ;  in  fact,  2  molecules 
hydrochloric  acid  correspond  to  i  molecule  sodium  oxide,  or  when 

2 


18  CHEMICAL-TECHNICAL    ANALYSIS. 

YZ  normal  hydrochloric  acid  is  used,  i  c.c.  of  the  latter  corresponds 
to  0.0155  gr.,  Na2O. 

If  the  addition  of  hydrochloric  acid  be  continued  in  the  presence 
of  methyl -orange  as  indicator,  a  permanent  red  coloration  sets  in 
only  when  all  the  alumina  has  redissolved.  Hence,  according  to 
the  formula, 

A12(OH)6  +  6HC1  =  A12C16  +  3H.2O, 

6  molecules  hydrochloric  acid  are  used  for  every  molecule  of  alu- 
mina, i  c.c.  %  normal  hydrochloric  acid,  therefore,  corresponds 
to  0.0085  gr-  alumina. 

To  accomplish  this  about  0.5  gr.  sodium  aluminate  is  dissolved 
in  hot  water  and  titrated  to  decolorization  with  ^  normal  hydro- 
chloric acid,  using  phenol-phthalein  as  indicator.  The  acid  used  is 
recorded,  1—2  drops  methyl -orange  are  added,  and  the  solution  is 
titrated  with  the  same  acid  until  it  assumes  a  permanent  red  color. 
The  calculation  of  the  amount  of  sodium  oxide  and  alumina  is  ex- 
plained by  the  above  statements. 

10.  Weldon  Mud. 

The  investigation  of  the  starting-products  for  the  manufacture  of 
chlorine,  pyrolusite,  as  well  as  bleaching-lime,  is  supposed  to  be 
known.  On  the  other  hand,  the  examination  of  Weldon  mud 
according  to  the  procedure  of  Lunge  will  be  described  more  fully. 
In  this  the  amount  of  manganese  dioxide,  the  total  manganese  and 
the  " basis"  are  determined. 

(a)  Manganese  dioxide.  An  acid  ferrous  iron  solution,  contain- 
ing 100  grs.  crystallized  ferrous  sulphate  (or  the  equivalent  amount 
of  ferrous  double  salt),  and  100  c.c.  pure  concentrated  sulphuric 
acid  to  the  liter,  is  accurately  titrated  with  one  half  normal  perman- 
ganate solution.  Thereupon,  25  c.c.  iron  solution  are  measured  off 
into  a  beaker  by  means  of  a  glass  pipette.  Ten  c.c.  of  the  well-agi- 
tated mud  are  drawn  into  a  pipette,  the  latter  is  washed  externally, 
the  contents  are  placed  with  the  iron  solution  in  the  beaker,  and  the 
adhering  mud  is  washed  out  into  the  latter.  When  all  has  dis- 
solved, on  agitation,  about  100  c.c.  water  are  added,  and  the  solu- 
tion is  then  titrated  with  the  permanganate  solution.  Let  the 
amount  of  the  latter  solution  —  y,  the  amount  of  permanganate 


WELDON    MUD.  19 

used   in  titrating   25  c.c.  iron  solution  =  x;  then  the  amount  of 
manganese  dioxide  per  liter  is  found  to  be  : 

2-175  (x-y)- 

(^)  Total  manganese.  Ten  c.c.  mud,  drawn  off  as  in  (a),  are 
boiled  with  cone,  hydrochloric  acid  until  chlorine  has  disappeared. 
Precipitated  chalk  is  then  added  to  neutralize  the  excess  of  acid. 
A  cone,  filtered  bleaching-lime  solution  is  added,  and  the  mass  is 
boiled  for  several  minutes,  after  which  the  red  color  which  appears 
is  removed  by  the  careful  addition  of  alcohol.  All  the  man- 
ganese is  precipitated  as  dioxide.*  This  is  filtered  off  and 
washed  until  the  filtrate  no  longer  reacts  with  potassium  iodide- 
starch  paper.  The  precipitate,  on  the  filter,  is  added  to  25  c.c.  of 
the  acid  iron  solution,  and  if  all  the  dioxide  refuses  to  dissolve,  an 
additional  25  c.c.  are  added.  One  hundred  c.c.  water  are  added, 
followed  by  titration  with  permanganate.  The  calculation  carried 
out  as  under  (cf)  gives  the  total  manganese  in  the  form  of  dioxide. 

(c)  Basis.  By  this  term  is  understood  the  monoxides,  etc. ,  con- 
tained in  the  mud,  which  react  with  hydrochloric  acid,  but  do  not 
generate  chlorine. 

Twenty-five  c.c.  (with  very  high  basis,  50  c.c.)  normal  oxalic 
acid  solution  are  diluted  to  about  xooc.c.  and  heated  to  60-80°  C. 
10  c.c.  manganese  mud  are  added  with  the  above  precautions,  and 
the  solution  is  shaken  until  the  precipitate  is  a  pure  white,  with  no 
yellow  tinge,  a  change  which  takes  place  rapidly  at  the  above  tem- 
perature. The  solution  is  diluted  to  202  c.c.  (2  c.c.  correspond  to 
the  volume  of  precipitate,  and  are  marked  on  a  200  c.c.  flask)  and 
100  c.c.  of  the  filtrate  are  titrated  back  with  sodium  hydrate,  using 
phenol  phthalein  as  indicator.  The  number  of  c.  c.  sodium  hydrate 
solution  used  =  z,  and  therefore  for  the  original  solution  =  2z. 

The  oxalic  acid  (i)  decomposes  the  manganese  dioxide,  yielding 
manganous  oxide  and  carbonic  acid;  (2)  binds  the  manganous 
oxide  liberated;  (3)  saturates  the  monoxides,  including  manganese 
oxide  originally  present ;  (4)  forms  an  excess  =  2z.  The  quanti- 
ties of  oxalic  acid  used  in  i  and  2  are  the  same,  and  together  equal 

*  When  completely  precipitated,  the  filtrate  will  not  turn  brown  on  adding 
bleaching-lime  solution. 


20  CHEMICAL-TECHNICAL   ANALYSIS. 

the  value  x — y  in  (#),  since  the  oxalic  acid  is  normal,  but  the  per- 
manganate only  half  normal.  The  value  3  represents  the  original 
amount  of  oxalic  acid  used,  less  the  quantity  (x — y)  used  in  i  and  2, 
and  the  excess  2z.  It  is  therefore  equal  to:  25 — x  -f-  y — 2z 
respectively  50 — x  -f  y — 2z. 

By  " basis"  is  understood  the  relation  of  the  value  of  3  to  a, 

v -y 

the  latter  expressed  by    •  — *   (since  the  alkali  is  normal  and  the 

permanganate  one -half  normal). 

When  25  c.c.  oxalic  acid  are  used,  therefore,  it  = 

25 — x  -f  y — 2z         50 — 2X  -f  2y — 4z  _      50 — 4Z 
x — y  x — y  x — y 

2 

and  when  <o  c.c.  oxalic  acid  are  used — 2 

x— y 

Boiler- Water. 

The  complete  analysis  of  a  water  used  for  technical  purposes 
embraces  the  following  determinations  :  Total  solids,  silica,  ferric 
oxide,  alumina,  lime,  magnesia,  alkali,  chlorine,  sulphuric  acid, 
carbonic  acid  and  nitric  acid.  In  addition  to  these,  nitrous 
acid  and  ammonia  may  be  qualitatively  tested  for.  If  necessary 
the  water  is  filtered  through  a  dry  filter  before  the  analysis. 

(a}  Total  solids.  500 — 1000  c.c.  water  are  evaporated  in  a 
weighed  platinum  dish  and  the  residue  is  dried  at  160 — 180°,  to  ap- 
proximately constant  weight.  It  may  be  remarked,  however,  that 
on  account  of  the  ready  decomposition  of  magnesium  salts,  partic- 
ularly magnesium  chloride,  on  the  one  hand,  and  the  difficulty  en- 
countered in  completely  expelling  all  the  water  of  crystallization 
from  gypsum  and  calcium  chloride,  on  the  other  hand,  the  results 
are  never  concordant. 

(<£)  Silica,  ferric  oxide,  alumina,  lime,  and  magnesia. 

One  liter  (sometimes  more)  water  is  evaporated,  with  hydrochloric 
acid,  in  a  porcelain  dish  ;  the  silica  is  separated,  ammonium  chloride 
is  added,  and  the  iron  and  alumina  are  precipitated  with  ammonia. 

In  presence  of  a  large  quantity  of  magnesia  the  precipitate  is 
dissolved,  re-precipitated,  and  both  constituents  are  ignited  and 
weighed  together. 

In  the  filtrate  the  lime  is  precipitated  with  ammonium  oxalate. 


BOILER-WATER.  21 

The  precipitate  is  then  carefully  heated  in  a  porcelain  crucible 
until  the  evolution  of  carbonic  acid  ceases,  and  is  then  ignited  over 
a  blast-lamp  to  constant  weight,  and  weighed  as  calcium  oxide. 
The  magnesia  is  then  precipitated  in  the  nitrate  with  sodium  hydro- 
gen phosphate  in  the  usual  manner. 

(c)  Alkalies.     These  are  determined  indirectly  in  the  total  solids 
by  weighing  the  sulphate  residue.     For  this  purpose  the  solids  are 
ignited  at  a  low  heat  in  the  platinum  dish,  and  then  dissolved  in 
dilute  hydrochloric  acid  under  cover  of  a  watch-glass.     The  mass 
is  finally  evaporated  with  10-12  drops  concentrated  sulphuric  acid, 
and  after  expelling  the  acid  it  is  ignited  and  weighed. 

If  then  the  sum  of  the  lime  and  magnesia,  previously  determined 
and  calculated  into  sulphates,  plus  the  quantities  of  silica,  ferric 
oxide  and  alumina  found,  be  subtracted  from  the  sulphate  residue, 
there  remain  the  alkali  sulphates  present,  which  are  considered  as 
sodium  sulphate  and  are  calculated  into  sodium  oxide. 

(d)  Chlorine.      Depending  on   the   result  of  a  qualitative   test, 
i^-i   liter  water,  after  concentration,  is  acidified  with  nitric  acid 
and  precipitated  in  the  usual  manner  with  silver  nitrate. 

(e)  Sulphuric  acid.      %— i  liter  water,  acidified  with  hydrochloric 
acid,  and,  if  necessary,  concentrated,  is  precipitated  with  barium 
chloride  in  the  usual  manner. 

(/")  Carbonic  acid.  The  combined  carbonic  acid  present  is 
estimated  in  ^-i  liter  by  adding  methyl -orange  and  titrating  to 
red  coloration  with  iV  normal  hydrochloric  acid.  The  calculation 
is  made  as  normal  carbonate  ;  hence  2HC1  =  iCO2.  The  estima- 
tion of  free  carbonic  acid  in  a  technical  analysis  may  be  omitted. 

(g)  Nitric  acid.  The  qualitative  test  is  best  made  with  the  di- 
phenylamine  reaction.  (See  Sulphuric  Acid.)  For  quantitative  esti- 
mation the  method  of  Schulze-Tiemann  is  best  employed.  In  this, 
by  means  of  ferrous  chloride  and  hydrochloric  acid,  the  nitric  acid 
is  reduced  to  nitric  oxide,  and  the  latter  is  determined  volumetric- 
ally.  The  details  are  too  well  known  to  describe.* 

The  qualitative  test  for  nitrous  acid,  of  which  only  minute  quan- 
tities are  present,  is  best  made  by  the  reaction  of  Griess.  A  small 
quantity  of  sulphanilic  acid  solution  (5  grs.  in  150  c.c.  dilute  acetic 

*  See  also  Fresenius,  Quantitative  Analysis,  Vol.  II.,  p.  155. 


22  CHEMICAL-TECHNICAL    ANALYSIS. 

acid)  is  added  to  a  small  quantity  of  the  water  in  a  test-tube  and 
warmed  to  80°,  when  a  solution  of  a-napthylamine  (.05  gr.  in  150 
c.c.  dilute  acetic  acid)  is  added.  In  the  presence  of  nitrous  acid  a 
red  coloration  ensues  either  immediately  or  after  a  few  minutes. 

To  test  for  ammonia  qualitatively  about  5  c.c.  Nessler's  reagent* 
are  added  to  100  c.c.  water,  and  the  change  noticed  from  above 
down  through  the  liquid.  Ammonia  causes  a  yellow  coloration. 
When  the  water  is  very  hard  or  chalybeate,  it  is  better  to  precipitate 
first  with  pure  caustic  soda  and  subsequently  examine  the  filtrate. 

Arrangement  of  results. — Chlorine  is  bound  to  sodium  and  any 
remainder  to  calcium.  Sulphuric  acid  is  bound  to  lime,  nitric  acid 
to  ammonia,  any  residue  to  sodium,  providing  the  chlorine  has  not 
fully  used  up  the  latter,  otherwise  to  magnesia.  The  remaining 
lime  and  magnesia  are  bound  to  carbonic  acid  in  the  form  of 
carbonates. 

Silica  is  expressed  as  such. 

Shorter  Procedure. 

It  is  often  desirable  to  circumvent  the  execution  of  a  complete 
analysis  by  the  use  of  a  shortened  procedure,  which  allows  a  more 
or  less  complete  insight  into  the  composition  of  a  water. 

As  such  the  method  of  Kalmann  and  the  direct  determination  of 
hardness  according  to  Clark  are  described. 

The  method  of  Kalmann  limits  itself  to  the  following  determi- 
nations : 

(a)  Combined  carbonic  acid.  This  is  ascertained  by  the  process 
described  under  (/)  in  the  complete  analysis. 

(V)  Lime.  This  is  determined  by  the  direct  precipitation  of  a 
measured  volume  of  water  by  means  of  ammonium  oxalate.  The 
separation  of  the  silica,  ferric  oxide  and  alumina  is  not  necessary. 

(?)  Magnesia  is  determined  in  the  filtrate  from  (&}  by  the  usual 
precipitation  with  sodium  hydrogen  phosphate. 

The  various  results  are  reckoned  on  i  liter  water.     On  the  basis 

*  To  prepare  this,  50  grs.  potassium  iodide  are  dissolved  in  50  c.c.  hot  water 
and  to  it  is  added  a  hot  concentrated  mercuric  chloride  solution  until  the  precipi- 
tate of  mercuric  iodide  formed  no  longer  dissolves.  The  solution  is  filtered,  150 
grs.  caustic  potash  in  concentrated  solution  are  added,  and  the  whole  is  diluted  to 
one  liter.  An  additional  5  c.c.  mercuric  chloride  solution  are  added,  the  solution 
is  allowed  to  settle,  and  the  clear  supernatant  liquid  is  poured  off. 


BOILER-WATER.  23 

of  these  results  the  preparation  of  water  for  technical  uses  can  be 
made.  This  will  subsequently  be  described  more  fully. 

Estimation  of  hardness  according  to  Clark. — The  hardness  of  a 
water  depends  on  the  amount  of  calcium  and  magnesium  salts  present. 
It  is  divided  into  temporary  hardness,  due  to  bicarbonates  of  calcium 
and  magnesium,  which  disappears  in  consequence  of  the  precipita- 
tion of  the  insoluble  monocarbonate  when  the  water  is  boiled,  and 
permanent  hardness,  which  is  due  to  any  remaining  calcium  and 
magnesium  salts.  Temporary  and  permanent  hardness  represent 
the  total  hardness  of  water. 

The  hardness  of  water  is  expressed  in  degrees  which  are  distin- 
guished as  German,  French  and  English  degrees  of  hardness.  The 
German  degrees  represent  the  number  of  milligrammes  calcium 
oxide  in  100  c.c.  water.  Any  magnesium  oxide  is  hereby  reck- 
oned in  the  form  of  the  equivalent  amount  of  calcium  oxide. 
French  degrees  state  the  equivalent  amount  of  calcium  carbonate, 
whereas  English  degrees  of  hardness  express  the  number  of  milli- 
grammes calcium  carbonate  contained  in  70  parts  water.  German, 
French  and  English  degrees  of  hardness  stand  in  the  ratio  of  .56  : 
11.70.  As  a  rule,  the  result  is  expressed  in  German  degrees. 

The  method  of  Clark  depends  on  the  fact  that  soap  solutions  pre- 
cipitate all  calcium  and  magnesium  salts  in  the  form  of  insoluble 
soaps.  A  slight  excess  of  soap  is  recognized  by  the  permanent 
lather  formed  on  the  liquid  on  shaking. 

Preparation  of  the  normal  soap  solution. — 10  grs.  finely-shaved 
Marseilles  soap  are  dissolved  in  i  liter  95  per  cent,  alcohol.  The 
solution  is  filtered,  and  to  every  200  grs.  solution  a  mixture  of  150 
c.c.  water  and  130  grs.  alcohol,  above  strength,  is  added.  The 
solution  so  obtained  is  now  standardized  in  such  a  manner  that  45 
c.c.  correspond  to  12  degrees  hardness.  To  accomplish  this  a 
solution  of  normal  hardness  is  prepared  which  contains  12  mg. 
calcium  oxide  in  100  c.c.  or  an  equivalent  quantity  of  barium  oxide. 
Such  can  be  made  by  dissolving  .3686  gr.  selenite  (CaSO4+2H2O) 
or  .523  gr.  pure  crystallized  barium  chloride  in  i  liter  distilled 
water.  To  100  c.c.  of  this  hard  water  in  a  glass-stoppered  flask  of 
about  200  c.c.  capacity,  the  soap  solution  is  added  from  a  burette 
until  a  thick  froth  lasting  five  minutes  just  forms  on  the  surface  on 
shaking.  Should  less  than  45  c.c.  of  the  soap  solution  be  used,  as 


24  CHEMICAL-TECHNICAL    ANALYSIS. 

is  usually  the  case,  then  from  the  result  obtained  in  the  titration 
the  dilution  of  the  alcohol  and  water  soap  mixture,  necessary  to  bring 
the  solution  to  the  required  strength,  is  calculated.  After  the  proper 
dilution  a  second  titration  is  made.  Should  this  not  yield  the  de- 
sired result,  the  above  process  is  repeated. 

Determination  of  the  hardness. — For  every  determination  100 
c.c.  of  the  water  must  be  used.  However,  since  the  soap  solution 
is  suitable  only  for  waters  possessing  a  hardness  up  to  12°,  and 
since  also  the  end  reaction  is  more  easily  recognized  in  waters  mod- 
erately hard,  it  is  advisable  to  use  only  50  c.c.  of  a  very  hard 
water  and  dilute  the  same  with  distilled  water  to  100  c.c.  The 
water  is  placed  in  a  stoppered  flask  as  before,  the  soap  solution 
is  then  added  from  a  burette,  and  the  liquid  is  shaken.  In  the 
place  of  the  above-mentioned  end  reaction,  Kalmann  calls  atten- 
tion to  the  nature  of  the  lather  and  the  perceptible  sound  pro- 
duced on  shaking.  The  lather  should  remain  firm,  that  is,  the 
bubbles  should  not  break  immediately  after  shaking.  The  sound 
becomes  dull  and  is  not  as  clear  as  that  produced  by  water  enclosed 
in  glass. 

It  often  happens  that  after  binding  the  lime  with  the  fatty  acids 
of  the  soap,  the  froth  becomes  firm  and  the  sound  becomes  muf- 
fled. The  reading  is  made  at  this  point,  and  more  soap  solution  is 
added.  No  further  change  should  take  place  if  the  end  reaction 
has  been  reached.  When  the  hardness  due  to  magnesia  is  not  yet 
neutralized,  the  bubbles  will  again  become  frail  and  the  sound  clear. 
In  this  case  the  titration  is  carried  further  until  the  end  reaction 
is  reached.  The  phenomenon  is  so  characteristic  that  at  times  it 
permits  of  an  approximately  quantitative  estimation  of  lime  and 
magnesia. 

Since  the  relation  is  not  constant  between  soap  solution  used  and 
hardness,  use  must  be  made  of  the  following  table.  The  hardness 
found  is  to  be  estimated  on  100  c.c.  of  the  original  water. 

The  method  of  Clark  gives  the  total  hardness.  Should  it  be  nec- 
essary to  determine  also  the  temporary  hardness,  ^-i  liter  water 
is  titrated  with  TV  normal  hydrochloric  acid,  using  methyl -orange 
as  indicator,  and  the  amount  of  acid  used  is  computed  as  lime.  The 
amount  of  lime  in  100  c.c.  represents  the  total  hardness.  The  per- 
manent hardness  is  gotten  by  difference. 


BOILER-WATER. 


25 


Table  of  German  Degrees.* 


c.c. 
Soap- 
solution. 

Hard- 
ness. 

c.c. 
Soap- 
solution. 

Hard- 
ness. 

c.c. 
Soap- 
solution. 

Hard- 
ness. 

c.c. 
Soap- 
solution. 

Hard- 

ness. 

c.c. 
Soap- 
solution. 

Hard- 
ness. 

1.8 

O.  I 

ii.  3 

2-5 

20.4 

4.9 

29.1 

7-3 

37-4 

9-7 

2.2 

0.2 

it-  7 

2.6 

20.8 

S-o 

29-5 

7-4 

37-8 

9-8 

2.6 

o-3 

12.  I 

2-7 

21.2 

5-1 

29.8 

7-5 

38.1 

9.9 

3-o 

0.4 

12.4 

2.8 

21.6 

5-2 

30.2 

7-6 

38.4 

10.0 

3-4 

o-5 

12.8 

2.9 

21.9 

5-3 

30.6 

7-7 

38.8 

10.  I 

3-8 

0.6 

13.2 

3-o 

22.3 

5-4 

30-9 

7-8 

39-i 

10.2 

4.2 

0.7 

13.6 

3-1 

22.6 

5-5 

31-3 

7-9 

39-5 

I0.3 

4-6 

0.8 

14.0 

3-2 

23.0 

5-6 

31-6 

8.0 

39-8 

10.4 

5-o 

0.9 

14.3 

3-3 

23-3 

5-7 

32.0 

8.1 

40.1 

10-5 

5-4 

.0 

14.7 

3-4 

23-7 

5-8 

32.3 

8.2 

40.5 

10.6 

5-8 

.1 

15.1 

3-5 

24.0 

5-9 

32.7 

8-3 

40.8 

10.7 

6.2 

.2 

15-5 

3-6 

24.4 

6.0 

33-° 

8.4 

41.2 

10.8 

6.6 

•3 

15.9 

3-7 

24.8 

6.1 

33-3 

8.5 

41-5 

10.9 

7.0 

•4 

16.2 

3-8 

25-1 

6.2 

33-7 

8.6 

41.8 

II.  0 

7-4 

•  5 

16.6 

3-9 

25-5 

6-3 

34-0 

8.7 

42.2 

11.  i 

7.8 

.6 

17.0 

4.0 

25.8 

6-4 

34-4 

8.8 

42-5 

II.  2 

8.2 

•7 

17.4 

4-i 

26.2 

6.5 

34-7 

8.9 

42.8 

H-3 

8.6 

.8 

17.7 

4.2 

26.6 

6.6 

35-° 

9.0 

43-1 

ii.  4 

9.0 

•9 

18.1 

4-3 

26.9 

6-7 

35-4 

9.1 

43-4 

ii  5 

9-4 

2.0 

18.5 

4.4 

27-3 

6.8 

35-7 

9.2 

43-8 

ii.  6 

9-8 

2.1 

18.9 

4-5 

27.6 

6.9 

36.1 

9-3 

44.1 

11.7 

10.2 

2.2 

19-3 

4.6 

28.0 

7.0 

36.4 

9-4 

44-4 

ii.  8 

10.6 

2-3 

19.7 

4-7 

28.4 

7-1 

36.7 

9-5 

44-7 

ii.  9 

II.  0 

2.4 

20.0 

4.8 

28.8 

7.2 

37-1 

9.6 

45  -° 

12.  0 

Preparation  of  Water  for  Technical  Purposes. 

In  this  the  precipitation  of  constituents  of  the  water  which  cause 
hardness  is  aimed  at.  Of  the  different  methods  proposed  for  the 
purpose,  only  the  very  useful  method  of  Stingl  and  Berenger  will 
be  more  fully  described. 

According  to  this  procedure  there  are  precipitated  : 

1.  The  bicarbonate  of  calcium  present  in  the  water,  by  means 
of  calcium  hydrate  or  sodium  hydrate.     For  every  molecule  cal- 
cium bicarbonate,   i  molecule  calcium  hydrate  or  2  molecules  so- 
dium hydrate  are  necessary,  according  to  the  equations  : 

Ca  H2  (C03)2  -f  Ca  (OH)2  =  2  Ca  CO3  -f  2H2O  and 
Ca  H2  (CO3)2  4-  2  Na  OH  —  CaCO3  -f  Na2  CO3  +  2  H2O 

2.  The  bicarbonate  of  magnesium  by  the  same  precipitants,  of 


*  Taken  from  Kalmann's  Kurzer  Anleitung  zur  chem.  Untersuchung,  etc. 


26  CHEMICAL-TECHNICAL    ANALYSIS. 

which  double  the  quantities  must  be  taken  on  account  of  the  solu- 
bility of  normal  magnesium  carbonate,  which  is  thereby  precipi- 
tated as  hydrate. 

Mg  H2  (CO,),  +  2  Ca  (OH),  =  2  Ca  CO3  +  Mg  (OH),  +  2  H2O 

and 

Mg  H2  (C03)2  +  4  NaOH  =  2  Na2  CO3  -f  Mg  (OH),  +  2  H2O. 

3.  All  the  remaining  calcium  salts  with  sodium  carbonate,   of 
which  i  molecule  is  necessary  for  every  molecule  lime. 

Ca  Cl,  +  Na2  CO3  =  Ca  CO,  +  2  Na  Cl. 

4.  All  remaining  magnesium  salts  with  caustic  soda.     For  every 
molecule  MgO,  2  molecules  Na  OH  are  needed. 

Mg  Cl,  +  2  Na  OH  =  Mg  (OH),  +  2  Na  Cl. 

Evidently,  it  follows  from  i  and  2  that  when  sodium  hydrate  is 
used  for  precipitation,  an  equivalent  amount  of  sodium  carbonate 
is  formed  in  solution,  which  at  times  may  precipitate  the  whole  of 
the  lime  salts  present.  From  this,  given  the  precipitants  men- 
tioned, the  three  following  conditions  may  be  deduced  : 

(a)  The  quantity  of  soda  is  greater  than  that  required  by  ( j)  to 
precipitate  the  calcium  salt.  In  this  instance,  in  order  to  avoid 
the  formation  of  an  excess  of  sodium  carbonate,  an  equivalent  part 
of  the  sodium  hydrate  is  replaced  by  calcium  hydrate.  Therefore, 
the  preparation  requires  sodium  hydrate  and  calcium  hydrate. 

(V)  The  soda  formed  is  less  than  the  amount  required  for  the  pre- 
cipitation of  all  remaining  lime  salts.  The  purification  is  then  con- 
ducted with  use  of  caustic  soda  and  soda. 

(c)  The  soda  formed  is  equal  to  the  amount  required  for  the  pre- 
cipitation of  calcium  salts.  In  this  instance  only  caustic  soda  is 
necessary  for  purification. 

In  all  three  instances  the  quantity  of  caustic  soda  required  to 
precipitate  any  magnesia  not  present  as  bicarbonate  (4)  is  added. 

Calculation. — The  values  from  the  shortened  procedure  of  Kal- 
mann,  or  the  complete  analysis  for  bound  carbonic  acid,  total  lime 
and  total  magnesia,  are  calculated  into  equivalents  of  lime.  The 
results  so  obtained  will  be  : 


FUEL.  27 

for  bound  carbonic  acid  a  g  Ca  O 

for  total  lime  p  g  Ca  O 
for  total  magnesia  and  total  lime 

(total  hardness)  y  g  Ca  O 

The  difference  2a — /5  is  now  found.  Should  this  be  positive, 
there  is  present  the  condition  described  under  (a).  For  purification 
there  are  used:  (2 a — 3)  parts  by  weight  lime  (dissolved  in  800 
times  the  quantity  of  water),  and  an  amount  of  caustic  soda  equiva- 
lent to  (y — a)  parts  by  weight  lime.  Instead  of  using  prepared 
caustic  soda,  the  latter  can  be  produced  from  slaked  lime  and  soda. 
For  this  purpose  (y — a)  parts  by  weight  lime  and  the  equivalent 
quantity  of  soda  are  used. 

Should  the  difference  2  a — /?  prove  to  be  negative,  condition  b 
exists. 

For  purification  there  is  used  the  quantity  of  soda  equivalent  to 
the  difference  of  (y — a)  g.  lime,  and  (y-f « — j3)  g.  lime,  which  renders 
a  part  of  the  soda  caustic. 

Finally,  should  the  difference  2  a — /3=o,  condition  c  exists. 

For  purification,  a  quantity  of  caustic  soda  equivalent  to  (y — a] 
parts  by  weight  lime,  is  necessary.  This  may  be  prepared  by 
adding  to  (> — «)  parts  by  weight  lime,  as  in  the  case  a,  an  equiva- 
lent amount  of  soda.* 

12.  Fuel. 

The  methods  described  are  applicable  to  all  kinds  of  fuel — an- 
thracite, bituminous,  lignite,  etc. 

As  a  rule,  the  determinations  made  in  a  coal  analysis  are  water, 
ash,  sulphur,  and  an  elementary  analysis.  In  addition  to  these, 
nitrogen  and  phosphorus,  as  well  as  the  yield  of  coke,  are  frequently 
estimated. 

(#)  Water.     The  estimation  of  water  in  fuel. 

The  sample  must  be  coarsely  ground,  about  pea  size,  since  during 
the  process  of  pulverization  considerable  moisture  is  given  off.  Coal, 
especially  anthracite  coal,  possesses  the  property  of  absorbing 
oxygen  upon  protracted  drying,  thereby  causing  an  increase  in 

*  The  derivation  of  these  methods  of  calculation  of  Kalmann  may  be  found  in 
the  Mittheilung  des  K.  K.  technolg.  Gewerbe  Museum,  1890. 


28  CHEMICAL-TECHNICAL    ANALYSIS. 

weight.  It  is  best  to  heat  about  20—50  grs.  material  in  a  weighing 
tube  provided  with  a  well -ground  stopper,  which  is  removed  during 
the  time  of  heating,  and  to  weigh  the  same  from  hour  to  hour  until 
no  further  loss  occurs.  Should  perhaps  the  last  weight  show  an  in- 
crease, the  previous  result  is  accepted. 

(^)  Ash.  The  ignition  is  best  carried  out  in  a  muffle,  when,  as  a 
rule,  one  hour  will  be  sufficient.  Should  a  muffle  not  be  accessible, 
about  i  gr.  finely -divided  coal  is  placed  in  a  small  platinum  capsule 
and  covered  with  the  lid  of  a  larger  crucible.  Heat  is  applied  at 
first  with  a  small  flame  to  avoid  sintering.  Later  the  lid  is  re- 
moved, the  capsule  is  tilted  on  the  triangle,  the  lid  is  likewise 
brought  into  an  inclined  position  on  the  capsule,  and  the  latter  is 
heated  protractedly  to  a  red  heat  with  an  ordinary-sized  flame. 
When  the  ash  appears  uniform,  which  is  usually  the  case  after  2-3 
hours,  the  capsule  is  weighed.  The  ash  is  now  moistened  with  a 
few  drops  of  alcohol,  when  any  particles  of  carbon  will  rise  to  the 
surface,  where  they  may  be  easily  recognized.  The  alcohol  is 
ignited  and  driven  off,  and  the  capsule  is  reweighed.  This  process 
is  finally  repeated  a  second  time.  Lunge  advises  the  use  of  a  plati- 
num crucible,  which  is  placed  in  the  round  opening  of  an  inclined 
asbestos  plate.  Only  the  part  of  the  crucible  protruding  beneath  is 
heated.  The  air  used  for  oxidation  does  not  admix  with  the  gases 
produced  by  the  flame,  and  therefore  acts  more  energetically. 

(V)  Sulphur.  Sulphur  is  present  in  fuels  in  the  form  of  sulphides 
(mostly  pyrite),  sulphates  (calcium  sulphate),  and  in  combination 
with  organic  substances.  The  estimations  usually  made  are  :  Total 
sulphur  and  sulphur  present  in  form  of  metallic  sulphides  +  sulphates. 
Sometimes  a  separate  determination  of  sulphur  due  to  sulphates  is 
also  made. 

Total  sulphur  according  to  Eschka.  About  i  gr.  finely-divided 
coal  is  thoroughly  mixed  in  a  platinum  crucible  by  means  of  a  thick 
platinum  rod,  with  1.5-2  grs.  of  an  intimate  mixture  of  2  parts  pure 
ignited  magnesia  and  i  part  anhydrous  sodium  carbonate.  The 
crucible  is  inclined  on  the  triangle,  or  in  the  perforated  asbestos 
plate,  without  a  lid,  and  the  lower  half  only  is  brought  to  a  red 
heat.  Heat  is  applied  for  about  i  hour,  with  frequent  stirring  by 
means  of  the  platinum  rod.  In  that  time  the  mass,  at  first  gray,  will 
have  assumed  a  bright  red  or  brown  color.  .  The  contents  are  cov- 


FUEL.  29 

ered  with  hot  water  and  rinsed  into  a  beaker,  the  crucible  is  boiled 
out  again,  and  bromine  water  is  added  until  the  liquid  assumes  a 
bright  yellow  color.  This  is  done  in  order  to  oxidize  any  remain- 
ing sulphides.  The  solution  is  heated,  filtered,  and  the  filtrate  is 
acidified  with  hydrochloric  acid.  It.  is  then  boiled  in  a  draught- 
chamber  until  the  deep  brown  colored  liquid  becomes  colorless,  and 
is  then  precipitated  with  barium  chloride. 

The  magnesia-soda  mixture  had  better  be  prepared  in  quantity. 
When  sulphur  is  present  in  small  quantity  in  this  mixture,  a  con- 
siderable portion  is  used  for  a  sulphur  determination,  and  the  corre- 
sponding quantity  of  the  latter  is  subtracted  from  the  total  sulphur. 

Sulphur  present  as  sulphides  and  sulphates.  According  to 
Drown,  a  saturated  solution  of  bromine  in  caustic  soda,  sp.  gr. 
1.25,  to  which  sufficient  caustic  soda  to  absorb  any  free  bromine 
has  been  added,  is  used  to  advantage  for  oxidation.  About  i 
gr.  of  the  finely  pulverized  substance  is  moistened  with  10  c.c.  of 
this  solution.  It  is  then  heated  and  acidified  with  hydrochloric  acid. 
In  the  space  of  10  minutes  two  quantities,  20  c.c.  each,  of  the  solu- 
tion, are  again  added,  and  each  time  the  solution  is  acidified  with 
hydrochloric  acid.  After  the  last  addition  of  acid,  the  mass  is  evap- 
orated to  dryness,  dried  at  iio°-ii5°  in  an  air-bath  to  convert 
silica  into  insoluble  form,  taken  up  with  hydrochloric  acid,  filtered, 
and  the  filtrate  is  precipitated  with  barium  chloride.  The  method 
is  especially  useful  for  anthracite  coal. 

Sulphate  sulphur. — A  considerable  quantity  of  the  sample  is  first 
incinerated,  and  a  weighed  quantity  of  the  ash,  2-3  grs.,  is  lixivi- 
ated with  hot  water.  In  order  to  oxidize  any  calcium  sulphide 
formed,  the  solution  is  boiled  with  hydrogen  peroxide  or  a  few  drops 
of  bromine.  It  is  then  acidified  with  hydrochloric  acid  and  pre- 
cipitated with  barium  chloride. 

(d)  Elementary  analysis.  The  execution  of  this  is  too  well 
known  to  describe.  It  is,  however,  necessary  to  add  special  pre- 
cautions pointed  out  by  Bockmann,  and  also  the  authors. 

While  the  estimation  of  hydrogen,  as  a  rule,  can  be  carried  out 
with  ease  and  accuracy,  a  difference  in  parallel  determination  of  y2 
to  24  Per  cent-  is  noticeable  in  determining  the  carbon,  even  when 
great  care  is  exercised.  The  reason  for  this  lies  in  the  already 
mentioned  tendency  of  carbon  to  sinter.  In  order  to  avoid  this  as 


30  CHEMICAL-TECHNICAL    ANALYSIS. 

much  as  possible,  it  is  advisable  to  conduct  the  first  part  of  the 
combustion  slowly.  This  can  be  accomplished  by  at  first  using  a 
current  of  air  (not  immediately  of  oxygen)  and  by  moderately  heat- 
ing the  portion  of  the  tube  in  proximity  to  the  substance.  It  is 
also  advisable  not  to  have  the  substance  too  finely  divided,  thereby 
avoiding  an  immediate  violent  action.  The  finish  of  the  preliminary 
step,  which  may  be  termed  coking,  is  easily  observed.  The  remain- 
ing operation  is  then  carried  out  at  a  high  heat  in  a  current  of  oxy- 
gen, the  flow  of  which  through  the  wash -bottle  is  regulated  to  about 
20  bubbles  in  every  10  seconds. 

Charging  the  combustion  tube  is  done  in  the  usual  manner.  For 
many  well-founded  reasons  it  has  been  found  decidedly  advantageous 
to  substitute  for  granular  copper  oxide  a  series  of  oxidized  copper 
spirals.  The  addition  of  a  silver  or  bright  copper  spiral  is  wholly 
unnecessary  on  account  of  the  minute  quantities  of  chlorine  and 
nitrogen.  On  the  other  hand,  an  absorbent  of  the  combustion- 
products  of  the  sulphur  is  absolutely  necessary.  In  the  absence  of 
such,  sulphurous  and  sulphuric  acid  readily  enter  the  absorption- 
bulbs,  are  absorbed,  and  increase  the  weight.  It  is  only  necessary, 
according  to  Fisher,  to  keep  the  oxide  of  copper  in  the  front  of  the 
tube  at  a  low  red  heat,  whereby  the  oxide  itself  acts  as  a  retainer  of 
the  combustion-products  of  sulphur.  Nevertheless,  it  appears  more 
advisable  to  fill  the  front  part  of  the  tube,  which  is  allowed  to 
protrude  about  28  cm.,  with  dry,  coarsely-divided  lead  peroxide. 
The  latter  is  placed  in  a  tin  case  provided  with  a  thermometer,  and 
is  heated  to  180°  during  the  combustion. 

Further,  be  it  noted  that  the  dehydrated  substance  had  best  be 
used,  and  that  a  hydrogen  determination  be  simultaneously  con- 
ducted. The  water  thus  found  is  deducted  from  the  total  water. 

(e)  Nitrogen.  The  method  is  found  under  the  accurately  de- 
scribed procedure  of  Kjeldahl  in  the  chapter  "  Fertilizers."  0.8— i 
gr.  finely-divided  coal  is  used  in  the  determination. 

(/)  Phosphorus.  This  is  always  determined  in  the  ash,  and  not 
the  original  substance.  1—2  grs.  ash,  obtained  best  by  ignition  in 
a  muffle,  are  digested  for  a  considerable  length  of  time  with  hydro- 
chloric acid  in  a  porcelain  dish,  whereby,  according  to  Muck,  the 
phosphorus  is  quantitatively  dissolved.  The  solution  is  evaporated 
to  dryness,  moistened  with  hydrochloric  acid,  and  100-150  c.c. 


FUEL.  31 

water  are  added.  It  is  warmed  on  a  water-bath,  filtered  into  a 
second  porcelain  dish,  and  evaporated  repeatedly  almost  to  dryness 
with  addition  of  nitric  acid.  The  liquid  is  diluted  with  water 
acidified  with  nitric  acid  and  precipitated  in  a  beaker  with  molyb- 
date  solution.*  The  remaining  treatment  is  carried  out  in  the 
well-known  manner  more  fully  described  in  the  chapter  on 
"Fertilizers." 

(g)  Coke,  i  gr.  finely-divided  coal  is  weighed  in  a  smooth- 
walled  platinum  crucible,  which  it  fills  to  the  height  of  30-35  mm., 
and  the  crucible  is  placed  on  a  thin  platinum  triangle  so  as  to  bring 
its  base  3  cm.  from  the  mouth  of  a  Bunsen  burner.  Strong  heat  is 
applied  to  the  tightly-closed  crucible  from  the  beginning.  The 
burner,  which  is  provided  with  a  protecting  cone,  should  have  a 
flame  18  cm.  in  height.  Heat  is  applied  until  no  luminous  flame 
issues  from  between  crucible  and  lid,  an  operation  lasting  1^-2 
minutes.  The  sooty  film  on  the  crucible-lid  is  also  weighed.  By 
following  these  directions  accurately  results  may  be  obtained  which 
agree  within  .2-.  4  per  cent. 

Arrangement  of  results. — The  results  are  as  frequently  based  on 
air-dried  as  on  dehydrated  material.  Oxygen  is  indirectly  deter- 
mined by  deducting  the  sum  of  the  water,  carbon,  hydrogen,  sul- 
phur,f  nitrogen  and  ash  found  from  100.  So  called  "  disponible 
hydrogen  ' '  is  that  which  remains  upon  deducting  the  quantity  of 
hydrogen  used  to  form  "chemically -bound  water"  with  the  oxygen, 
e.g. ,  y%  of  the  oxygen,  together  with  that  present  as  hygroscopic 
water,  from  the  total  hydrogen. 

Absolute  heating  value. — To  calculate  this,  the  formula  lately 
recommended  by  Schwackhofer  is  employed, 

SoooC  +  2o,oooH  +  2qooS-6ooW 

E  — -  calories, 

100 

in  which  the  symbols  C,  H,  S,  W  represent  the  percentages  of 
carbon,  "disponible"  hydrogen,  sulphur  and  water  (hygroscopic 
and  chemically  bound). 

If  the  absolute  heating  value  (E)  be  divided  by  637,  there  results 

*  Preparation,  see  under  V,  "Fertilizers." 
f  Excluding  sulphur  existing  as  sulphate. 


32 


CHEMICAL-TECHNICAL    ANALYSIS. 


the  evaporative  efficiency,  that  is,  that  weight  of  water  at  o°  which 
is  changed  to  steam  at  100°  by  one  kilogram  of  coal. 

13.  Furnace  Gases. 

The  investigation  of  gases  of  a  furnace  serves  to  regulate  the  feed- 
ing of  the  latter.  Carbonic  acid,  oxygen,  carbon  monoxide  and 
nitrogen,  the  latter  by  difference,  are  determined  in  furnace  gases. 
For  this  purpose  the  apparatus  of  Orsat,  whose  arrangement  is  seen 
in  the  following  illustration,  Fig.  3,  is  best  used : 


FiG.  3. — Orsat's  Apparatus. 

The  gas  burette  A  is  bound  to  the  leveling  flask  B,  which  is  filled 
with  water.  By  raising  B,  A  is  filled  with  water  to  the  uppermost 
mark ;  by  lowering  B  gas  is  drawn  through  the  tube  C,  or  from  the 
absorption  vessels  D,  E,  F;  by  repeatedly  raising  B,  simultaneously 
opening  the  stopcocks  of  D,  E  or  F,  the  gas  may  be  led  into  any 
of  the  latter.  To  establish  the  necessary  communications  the  cocks 
D,  £,  F,  and  the  three-way  cock  A  are  provided.  In  order  to  in- 
crease absorption  the  vessels  £>,  E  and  F  are  provided  with  a  large 


FURNACE    GASES.  33 

number  of  narrow  glass  tubes.  D  is  used  to  absorb  carbonic  acid, 
and  is  filled  with  no  c.c.  caustic  potash  solution  (sp.  gr.  1.20-1.8). 
E  serves  to  absorb  oxygen,  and  contains  pyrogallic  acid  or  thin 
phosphorus  sticks  immersed  in  water.  In  the  latter  case  black 
paper  surrounds  the  vessel  to  protect  the  contents  from  the  action 
of  light.  Finally,  for  the  absorption  of  carbon  monoxide,  the  vessel 
Fis  filled  with  cuprous  chloride  solution  prepared  by  shaking  200 
grs.  commercial  cuprous  chloride  with  a  solution  of  250  grs.  am- 
monium chloride  in  750  c.c.  water  in  a  stoppered  flask,  into  which 
there  is  placed,  later,  a  copper  spiral  which  reaches  to  the  bottom. 
Before  using,  i  vol.  ammonia  (sp.  gr.  0.905)  is  added  to  3  vols.  of 
this  solution.  Complete  absorption  takes  place  only  upon  pro- 
longed contact ;  and,  furthermore,  the  reagent  must  be  frequently  re- 
newed. The  absorption  reagents  are  kept  in  the  rear  tubes,  and 
are  brought  into  those  in  front  only  when  the  apparatus  is  in  use. 
This  is  accomplished  by  establishing  communication  with  the  out- 
side air  by  means  of  stopcock  #,  closing  d,  e  and  /,  filling  A 
with  water  by  raising  B,  arranging  a  to  close  off  A,  lowering  B 
and  opening  the  stopcock  d.  The  liquid  is  thereby  drawn  from  the 
rear  into  D.  In  a  similar  manner  E  and  F  are  filled.  The  tube 
c,  previously  provided  with  a  U  tube,  enclosing  raw  cotton  to 
exclude  dust,  is  now  connected  with  the  chamber  from  which  the 
gas  is  to  be  taken,  and  by  closing  d,  e  and  f  and  lowering  B,  a 
volume  of  gas  sufficient  to  fill  to  the  zero  point  is  drawn.* 

The  cock  d  is  opened,  B  is  raised,  and  the  gas  in  the  burette  is 
forced  into  Z>.  As  soon  as  the  water  reaches  the  end  division  the 
flask  is  lowered,  and  the  process  is  quickly  repeated  in  order  to 
bring  the  gas  into  thorough  contact  with  the  reagents.  Finally  the 
water-levels  in  flask  and  burette  are  brought  to  the  same  height,  the 
stopcock  d  is  closed,  and  the  volume  is  read.  The  decrease  in 
volume  gives  per  cent,  by  volume  of  carbonic  acid,  since  the  bu- 
rette is  divided  into  100  c.c.  In  the  same  manner  the  oxygen  is 
subsequently  determined  by  absorption  in  £,  the  carbon  monoxide 
in  F,  and  the  nitrogen  as  remainder  of  100. 


*  To  completely  remove  air  contained  in  the  tubes,  the  gas  forced  in  by  lower- 
ing B  is  passed  out  through  exit  in  a,  fresh  gas  is  drawn  in,  and  the  process  is 
repeated. 

3 


34  CHEMICAL-TECHNICAL   ANALYSIS. 

For  gases  rich  in  hydrogen,  such  as  water-gas,  the  apparatus  of 
Orsat-Lunge  is  used.  The  latter  is  quite  similar  to  the  Orsat  appa- 
ratus. The  gas,  freed  from  carbonic  acid,  oxygen  and  carbon 
monoxide,  is  mixed  with  a  measured  quantity  of  air,  and  is  con- 
ducted through  a  capillary  containing  platinum  asbestos  or  palla- 
dium asbestos.  By  heating  the  latter  the  hydrogen  is  burned.  The 
residue  is  again  measured  in  the  burette,  and  ^  the  decrease  in 
volume  is  reckoned  as  hydrogen.  (2  vols.  hydrogen  unite  with  i 
vol.  oxygen,) 


II.  Cement  and  Clay. 


THE  raw  materials  for  the  products  of  this  group  are  limestone, 

marl  and  clay. 

1.  Lime. 

(a)  Moisture.  3-5  grs.  sample  are  heated  to  constant  weight 
in  a  drying  oven  at  no0— 120°. 

(<£)  Silica  and  clay,  ferric  oxide,  alumina,  lime  and  magnesia. 
About  i  gr.  powdered  sample  is  uniformly  moistened  with  water 
in  a  porcelain  dish,  covered  with  a  watch-glass,  and  decomposed  by 
addition  of  moderately  dilute  hydrochloric  acid.  After  the  evo- 
lution of  carbonic  acid  has  ceased  the  mass  is  evaporated  to  dry- 
ness  on  a  water-bath  with  constant  stirring,  completely  dried  by 
heating  on  an  asbestos  plate,  and  covered  with  sufficient  concen- 
trated hydrochloric  acid  to  completely  dissolve  all  soluble  matter. 
After  a  half-hour  hot  water  is  added,  the  solution  is  filtered,  the 
precipitate  is  washed  and  weighed  as  silica  and  clay.  To  the  hot 
filtrate,  which  has  been  oxidized  with  bromine  water,  ammonia  is 
added  to  slight  excess,  the  solution  is  boiled  for  a  few  moments,  and 
the  precipitate  formed  is  filtered  off.  To  free  it  from  any  adhering 
lime,  the  solution  in  hydrochloric  acid  and  precipitation  with  am- 
monia may  be  repeated.  Ferric  oxide  and  alumina  are  determined 
together.  A  separate  iron  determination,  when  necessary,  is  con- 
ducted in  another  portion.  The  filtrate,  now  about  200  c.c.  in 
volume,  is  brought  to  incipient  boiling,  the  flame  is  removed,  and 
ammonium  oxalate  is  added  to  the  point  of  complete  precipitation 
and  rapid  deposition.  A  sufficient  excess  of  ammonium  oxalate  is 
yet  added  to  convert  all  magnesia  into  soluble  magnesium  oxalate. 
Finally  the  solution  is  diluted  to  400—500  c.c.  and  allowed  to  stand 
several  hours  in  a  warm  place.  Frequently  magnesia  is  thrown 
down  together  with  the  lime,  but  by  gradual  addition  of  the  ammo- 
nium oxalate  the  magnesia  can  be  reduced  to  about  .02  per  cent. 
If  exact  results  be  required,  the  precipitation  may  be  repeated  a 
second  time. 


36  CHEMICAL-TECHNICAL   ANALYSIS. 

For  this  purpose  the  clear  liquid  is  decanted  through  a  filter,  the 
residue  remaining  in  the  beaker  is  stirred  twice  with  hot  water,  and 
the  clear  liquid  is  decanted  each  time  through  the  same  filter.  The 
precipitate  in  the  beaker  is  redissolved  in  hydrochloric  acid,  and  to 
the  solution  ammonia  and  ammonium  oxalate  are  added  in  suffi- 
cient quantity.  The  reprecipitated  calcium  oxalate  is  allowed  to 
stand  one  hour.  The  solution  is  then  filtered  through  the  same 
filter,  the  latter  is  washed  thoroughly  with  hot  water,  dried,  ignited 
for  a  time  at  a  low  heat,  and  is  then  ignited  over  a  blast-lamp  until 
constant  weight  is  obtained.  It  is  weighed  as  calcium  oxide.*  The 
filtrate  from  the  lime  is  made  slightly  acid  with  hydrochloric  acid 
and  is  concentrated  on  a  water-bath  to  about  one-third  its  volume. 
One-third  the  remaining  volume  of  dilute  ammonia  is  added,  and 
when  cool  the  magnesia  is  precipitated  with  sodium  hydrogen 
phosphate.  After  three  hours  the  solution  may  be  filtered.  The 
precipitate  is  washed  with  water  containing  about  3  per  cent, 
ammonia,  then  dried  and  ignited  in  a. platinum  crucible.  The 
weight  represents  Mg2  P2  Or 

(V)   Oxide  of  iron  and  sulphuric  acid. 

Both  constituents  may  when  necessary  be  determined  in  the  same 
operation.  For  this  purpose  about  10  grs.  powdered  sample  are 
placed  in  a  250  c.c.  flask,  dissolved  in  hydrochloric  acid,  and 
diluted  to  the  mark.  Two  hundred  c.c.  solution  are  filtered 
through  a  dry  filter  and  precipitated  with  ammonia.  The  precipi- 
tate formed  is  dissolved  in  sulphuric  acid  (i  14),  diluted  with  water, 
reduced  with  zinc  and  titrated  with  permanganate  of  potash.  The 
filtrate  from  the  sesquioxide  of  iron  is  acidified  with  hydrochloric 
acid,  and  the  sulphuric  acid  is  determined  with  barium  chloride. 

(d*)  Carbonic  acid.  Carbonic  acid,  as  a  rule,  can  be  calculated 
by  considering  it  bound  to  the  calcium  oxide  and  magnesia  which 
remain  after  deducting  that  portion  of  the  former  attached  to  the 
sulphuric  acid  found.  When  large  quantities  of  silica  are  present — 
in  which  case  lime  can  exist  as  calcium  silicate — a  direct  determi- 
nation of  carbonic  acid  is  made  in  the  usual  manner  by  absorption 
in  tubes  containing  soda  lime. 


*  To  check  the  result,  it  is  advisable  to  titrate   the  calcium  oxide  with  hydro- 
chloric acid. 


MARL.  37 

(<?)  Alkali  metals  are  present  only  in  traces,  as  a  rule,  and  their 
estimation  may  be  omitted. 

(/)  Organic  matter.  For  an  approximate  result  the  method  of 
Fresenius  is  useful.  By  this  method  the  organic  matter  is  deter- 
mined by  combustion  in  a  current  of  oxygen.  For  every  58  parts 
carbon  obtained  (213  parts  carbonic  acid)  100  parts  organic  matter 
are  allowed. 

Marl. 

Limestones  containing  under  10  per  cent,  clay,  i.e.,  clay,  silica 
and  sesquioxides,  yield  "fat  lime"  on  being  calcined,  and  are 
suitable  for  the  preparation  of  lime  cements.  Limestones  contain- 
ing over  10  per  cent,  of  such  constituents  yield  "lean  lime." 
They  are  termed  argillaceous  limestones  or  marls.  A  further  dis- 
tinction is  made  between  calcareous  and  clayey  marls,  depending  on 
the  predominance  of  one  or  the  other  constituent. 

The  analysis  of  marl  is,  as  a  rule,  carried  out  in  the  manner  of  a 
limestone  analysis,  with  the  avoidance,  nevertheless,  of  too  great  an 
excess  of  hydrochloric  acid  and  excessive  heating  when  dissolving. 
In  addition,  a  determination  of  clay,  insoluble  in  hydrochloric  acid, 
is  made.  This  applies  mainly  to  the  determination  of  soluble  silica, 
coarse  and  fine  sand. 

(a}  Soluble  silica.  The  residue,  insoluble  in  hydrochloric  acid, 
obtained  from  1-2  grs.  sample,  is  removed  from  the  filter  and  lix- 
iviated by  boiling  several  times  with  renewed  portions  of  caustic 
soda  or  chemically  pure  soda  in  a  porcelain  or  platinum  dish  until 
the  filtrate  fails  to  show  silica  as  turbidity  upon  addition  of  ammo- 
.nium  chloride  followed  by  boiling.  The  silica  in  the  alkaline 
extractions  of  the  residue  is  determined  in  the  usual  manner  after 
precipitation  with  hydrochloric  acid  and  evaporation  to  dryness. 

(li)  Coarse  and  fine  sand.  Hydrochloric  acid  is  added  to  50  grs. 
substance.  The  solution  is  boiled  ^  hour,  and  the  residue  is  sub- 
jected to  the  washing  process  described  under  "Clay." 

The  investigation  of  marl  rich  in  clay  may  also  be  conducted  by 
the  method  described  under  "  Clay." 

Marls  which  contain  20-30  per  cent,  clay  are  best  suited,  on  the 
average,  for  the  preparation  of  hydraulic  cement.  On  the  other 
hand,  those  marls,  the  clay  in  which  contains  an  excessive  amount 
of  free  silica,  yield  only  ordinary  hydraulic  cements,  particularly 


38  CHEMICAL-TECHNICAL    ANALYSIS. 

when  the  latter  is  present,  for  the  greater  part,  as  common  sand 
and  not  powdered  sand.  Briefly,  the  more  the  clay  in  a  marl  is 
present  as  silicates,  not  free  silica,  and  the  less  coarse  sand  it  con- 
tains, the  better  hydraulic  cement  will  it  yield.  In  addition,  the 
requisite  proportion  of  clay  to  lime  must  be  present. 

By  mixing  clay  with  limestone  and  calcining  the  mixture  until 
sintered,  products  are  obtained  which,  upon  pulverizing,  possess 
the  properties  of  a  hydraulic  cement  and  are  known  as  Portland 
cement.  The  limestone  is  used  in  form  of  chalk  or  marl,  and 
should  not  contain  too  much  magnesia.  While  magnesia  to  an 
extent  of  3  per  cent,  operates  advantageously,  considerable  quanti- 
ties are  harmful,  and  about  18  per  cent,  has  a  decidedly  dis- 
advantageous effect  on  the  hardness  of  the  cement. 

The  clay  used  is  preferably  one  'containing  little  sand  (especially 
coarse  sand),  much  silica,  and  a  rather  high  amount  of  iron  oxide 
and  alkali.  Such  clays  are  usually  easily  fusible  and  show  the 
following  average  composition  : 

Percent. 

Silica,     .         ......     -»      •  .         ...         .         .         .  59-68 

Alumina,          »         ....        '...-,         .         .         .  12-23 

Ferric  oxide,   ....         .    •     .         .         .         .  7~I4 

Lime, .         .  -75-io 

Magnesia,         .         .         .      '  ,         .  ^.     .    ;"    .         .         .  1-3 

Alkali,    .       ;.         .         ,         T 2-4 

According  to  Michaelis,  it  is  preferable  that  the  proportion  of 
clay  to  lime  in  the  mixture  be  such  that  in  the  calcined  Portland 
cement  there  be  210—230  equivalents  of  alkaline  earths  and  15—25 
equivalents  clay,  plus  ferric  oxide,  to  80  equivalents  silicate. 

If  silica  and  sesquioxides  (as  acids)  be  reckoned  on  lime,  then 
the  following  expression  is  obtained : 

100  (SiO2.R2O3).  200  CaOand  100  (SiO2.R2O3).  240  CaO. 

Under  200  CaO  disintegration  occurs ;  above  240  spreading 
occurs,  and  it  is  advantageous  not  to  exceed  220. 

Kosmann  states  that  there  should  be  present  in  the  mixture 

6  Mol.  CaO  =60.21  per  cent. 
2     «    SiO2  =  21.50       " 
,1     "  A12O3=  18.29       " 


CLAY.  39 

But  on  account  of  the  presence  of  a  not  inconsiderable  quantity 
of  free  silica  in  the  limestone  and  clay,  the  above  proportion  must 
practically  be  increased  2^-2^  SiO2  and  decreased  .$-.66  A12O3. 

The  extreme  limits  in  the  composition  of  Portland  cements, 
according  to  Candlon,  are  : 

Per  cent. 

Lime, 58-67 

Silica.  .........         20-26 

Alumina,      .....          .          .  .  5-10 

Magnesia,    .         .         .         .          .         .         .         .         .          .5-3 

Sulphuric  Acid,    .         .          .         .         .          .         .         .          .5-2 

The  chemical  investigation  of  finished  cements  is  conducted  in 
exactly  the  same  manner  as  that  of  limestone  or  marl.  Frequently 
the  mere  determination  of  clay  (total  silicates)  is  required.  For 
this  purpose  2  grs.  cement  are  covered  in  a  capsule  with  20  c.c. 
water  and  decomposed  with  hydrochloric  acid,  to  which  nitric  acid 
has  been  added.  Thereupon  the  solution  is  brought  to  boiling, 
precipitated  with  ammonia,  and  the  precipitate  formed  is  weighed. 
Good  cement  should  dissolve  almost  completely  in  concentrated 
hydrochloric  acid,  since,  in  consequence  of  the  treatment  under- 
gone, the  silica  is  transformed  into  a  soluble  modification. 

3.  Clay. 

In  a  broad  sense  clay  is  understood  to  be  a  hydrated  aluminium 
silicate,  which  in  addition  to  argillaceous  matter  can  contain  among 
other  admixtures  unaltered  feldspar  and  silica,  frequently  also  iron, 
lime,  magnesia,  alkalies,  and  minute  quantities  of  manganous  oxide, 
as  well  as  volatile  constituents. 

Concerning  the  part  played  by  the  individual  constituents,  the 
following  may  be  stated  : 

Alumina  is  the  most  valuable  and  distinctive  constituent  of  clay. 
Its  quantity  regulates  the  physical  properties  of  clays  (plasticity, 
shrinking),  as  well  as  fusibility. 

Silica  frequently  operates  relatively  harmful  on  the  properties  of 
clay.  It  decreases  the  plasticity,  increases  the  point  of  fusibility, 
and  increases  the  action  of  fluxes  at  high  temperature.  It  is  con- 
tained in  clay,  chemically  as  well  as  mechanically  bound,  and  its 
analysis  in  latter  form  is  necessary. 

Magnesia,  lime,  ferric  oxide,  alkalies,  act  as  fluxes,  and  in  fact 


40  CHEMICAL-TECHNICAL    ANALYSIS. 

equivalent  amounts  of   these  exert  the  same  influence  upon  the 
fusibility.       Comparatively,    magnesia  ranks   first  as   a   flux,    lime 
second.     Alkalies  are  present  mostly  in  form  of  potassium  oxide 
and  are  reckoned  as  such.     Iron  influences  chiefly  the  tinge  of 
clay,  and  changes  the  color  as  in  the  false  coloring  of  pottery. 

Volatile  matter. — (Loss  on  ignition.)  This  is  caused  by  the  sul- 
phur, water,  carbonic  acid  and  organic  matter  present.  These, 
when  present  in  considerable  quantity,  can  influence  the  plasticity 
of  the  clay  as  well  as  the  density  after  baking.  Much  stress  is  to 
be  laid  on  the  quantitative  estimation  of  sulphur,  since  even  minute 
quantities  (in  form  of  pyrite)  can  act  harmfully.  The  chemical 
analysis  of  clay  is  divided  into  the  empirical -technical  and  rational 
analyses. 

A.  Empirical-technical  Analysis. 

(a)  Moisture.  2-5  grs.  sample  are  dried  to  constant  weight  at 
120°. 

(^)  Total  loss  on  ignition  (water  of  constitution,  organic  mat- 
ter and  carbonic  acid). 

One  to  2  grams  dried  sample  are  ignited  over  a  blast-lamp,  with 
air  access,  to  constant  weight. 

(£•)  Silica,  alumina,  ferric  oxide,  manganous  oxide,  lime  and 
magnesia.  About  i  gram  finely  pulverized  average  sample  is  dis- 
solved in  a  platinum  crucible  by  fusion  with  6-8  times  amount  so- 
dium potassium  carbonate  mixture. 

Under  no  circumstances  should  more  than  ten  times  the  amount 
be  used.  Michaelis  states  that  it  is  better  to  use  pure  sodium  car- 
bonate. In  this  case  fusion  sets  in  at  a  higher  temperature  and 
after  all  carbonic  acid  has  been  evolved.  Thereby  sputtering  is 
prevented.  The  fused  mass  is  disintegrated  with  water,  carefully 
acidified  with  hydrochloric  acid,  the  solution  is  evaporated  to  dry- 
ness,  and  the  silica  is  isolated  as  usual.  The  purity  of  the  latter  is 
finally  tested  with  hydrofluoric  acid.  After  addition  of  ammonium 
chloride,  when  the  estimation  of  manganese  is  not  taken  into  con- 
sideration, the  iron  and  alumina  in  the  filtrate  are  precipitated  in 
the  usual  manner  by  ammonia.  Should  a  separation  from  manga- 
nese be  required,  the  filtrate  is  as  nearly  as  possible  neutralized  with 
sodium  carbonate  and  boiled  a  short  time  with  a  concentrated  so- 
lution of  sodium  acetate  or  ammonium  acetate. 


CLAY.  41 

The  precipitate,  which  rapidly  settles  on  removing  the  heat,  is 
repeatedly  decanted  with  hot  water,  to  which  ammonium  acetate 
has  been  added.  It  is  then  thrown  on  the  filter  and  washed  with 
the  water  until  the  filtrate  no  longer  shows  traces  of  chlorine.  The 
precipitate  is  either  directly  dried  and  ignited,  or  again  dissolved  in 
hydrochloric  acid,  reprecipitated  and  filtered.  When  greater  accu- 
racy is  demanded,  the  filtrate  is  added  to  that  previously  obtained. 

Special,  care  is  also  to  be  taken  in  decanting  and  washing  the  pre- 
cipitate, even  when  no  attempt  is  made  to  separate  manganese. 

It  is  not  considered  superfluous  to  test  the  purity  of  the  precipi- 
tate, according  to  Mitscherlich,  by  dissolving  the  precipitate  so 
obtained  in  a  large  excess  of  a  mixture  of  8  parts  concentrated  sul- 
phuric acid  and  3  parts  water.  If,  upon  warming  in  a  flask,  flakes 
of  silica  appear,  the  latter  is  filtered,  weighed,  the  weight  deducted 
from  that  of  the  alumina  -j-  ferric  oxide  and  added  to  that  of  the 
silica.  The  iron  in  the  filtrate  can  be  determined,  after  reduction 
with  chemically  pure  zinc,  by  means  of  pure  permanganate.  Should 
the  test  of  the  alumina-ferric  oxide  precipitate  be  unnecessary,  an 
aliquot  portion  is  finely  pulverized  in  an  agate  mortar  and  fused  in 
a  platinum  crucible  with  bisulphate  of  potash,  at  first  with  a  low 
heat  and  finally  at  a  red  heat.  The  fusion  is  dissolved  in  water, 
sulphuric  acid  is  added,  and  the  iron  after  reduction  with  zinc  is 
titrated. 

In  the  filtrate  from  the  alumina  and  ferric  oxide  the  manganese  is 
eventually  estimated  as  dioxide  by  adding  bromine  water  to  the  cold 
solution,  weakly  acid  with  acetic  acid,  saturating  with  ammonia  and 
filtering  off  the  precipitate  formed  on  boiling  briskly.  The  filtrate, 
acidified  with  hydrochloric  acid,  is  boiled  down,  an  excess  of  am- 
monia is  added,  the  lime  is  precipitated  with  oxalate  of  ammonia  as 
usual,  and  the  magnesia  with  sodium  hydrogen  phosphate. 

(V)  Alkalies.  Two  grams  finely  divided  clay,  mixed  with  a 
little  water  in  a  platinum  dish,  are  covered  with  concentrated 
sulphuric  acid  ;  hydrofluoric  acid  is  added,  and  the  mass  is  warmed 
on  a  water-bath  until  all  hydrofluoric  acid  has  volatilized.  Thereupon 
the  sulphuric  acid  is  almost  completely  expelled,  and  the  residue  is 
covered  with  hot  water  and  hydrochloric  acid.  Thereby  the  resi- 
due may  be  carbonized,  but  at  no  time  should  it  be  gritty.  Sulphuric 
acid,  alumina,  ferric  oxide  and  magnesia  are  now  precipitated  with 


42  CHEMICAL-TECHNICAL    ANALYSIS. 

an  excess  of  concentrated  baryta  water.  Excess  of  baryta  in  the  fil- 
trate is  precipitated  with  sulphuric  acid  ;  ammonia,  carbonate  and 
oxalate  of  ammonia  are  then  added,  and  the  whole  is  allowed  to  stand 
for  some  time.  The  filtrate  is  evaporated  to  dryness  in  a  weighed 
platinum  dish.  It  is  then  heated  in  an  air-bath,  then  over  a  small 
flame  to  expel  ammonium  salts,  and  is  finally  ignited.  The  ignited 
residue  is  treated  with  water,  and  in  event  of  incomplete  solution  it 
is  treated  in  the  same  manner  as  before,  with  small  quantities  of 
ammonia,  carbonate  and  oxalate  of  ammonia. 

This  operation,  repeated  two  or  three  times,  suffices  to  obtain  the 
alkali  sulphates  in  perfectly  pure  state.  They  are  considered  as 
potassium  sulphate,  from  which  potassium  oxide  is  calculated. 

(e)  Sulphur.  5  grs.  clay  are  mixed  with  powdered  chlorate  of 
potash ;  concentrated  nitric  acid  is  gradually  added  \  the  mass  is 
slightly  heated  and  finally  boiled  with  repeated  additions  of  hydro- 
chloric acid  until  all  nitric  acid  is  decomposed.  The  excess  of  acid 
is  then  evaporated,  water  is  added,  and  the  sulphuric  acid  is  pre- 
cipitated with  barium  chloride. 

B.  Rational  Analysis. 

The  purpose  of  this  is  not  to  determine  individual  constituents 
present,  but  rather  to  classify  the  same  as  distinct  characteristic 
compounds.  The  amounts  of  argillaceous  matter — quartz,  feldspar, 
chalk,  etc. — are  determined  thereby.  The  operation  is  mostly  ap- 
plied to  pure  clays  for  porcelain  and  pottery. 

To  do  this,  5  grs.  substance  are  softened  in  a  porcelain  dish  with 
about  100—150  c.c.  water,  and  boiled  with  addition  of  2  c.c.  caustic 
soda,  whereby  a  fine  state  of  division  is  obtained.  Upon  cooling, 
about  25  c.c.  concentrated  sulphuric  acid  are  added,  after  which 
the  contents  of  the  covered  vessel  are  kept  in  a  state  of  brisk 
ebullition  until  sulphuric  acid  begins  to  volatilize.  In  conse- 
quence, beside  the  transformation  of  chalk  to  calcium  sulphate, 
only  the  clay  matter  (silicate  of  alumina)  is  decomposed,  whereas 
quartz  and  feldspar  remain  unattacked.  The  mass  as  obtained  is 
separated  from  the  greater  part  of  the  sulphuric  acid  and  sulphate 
of  aluminium  by  dilution  with  water  and  decantation.  It  is  then 
twice  extracted  alternately  with  very  concentrated  caustic  soda  and 
hydrochloric  acid.  Each  time  it  is  filtered  upon  the  same  filter 


ANALYSIS    BY    MECHANICAL    MEANS. 


43 


upon  which  the  whole  residue  is  finally  thrown,  washed  with  hydro- 
chloric acid,  ignited  and  weighed.  The  residue  consists  only  of 
feldspar  and  quartz.  The  loss  in  weight  is  clay  and  carbonate  of 
lime.  The  amount  of  the  latter  is  ascertained  by  means  of  a 
carbonic  acid  determination. 

The  mixture  of  quartz  and  feldspar  is  decomposed  |L 

with  sulphuric  acid  and  hydrofluoric  acid.  In  the 
filtrate  the  alumina  is  estimated  by  precipitation  with 
ammonia,  redissolving  and  reprecipitating,  and  from 
the  result  the  feldspar  is  estimated  (i  part  alumina  = 
5.41  parts  feldspar).  Quartz  is  found  by  difference. 


C.  Analysis  by  Mechanical  Means 
(Suspension). 

Among  the  apparatus  employed,  that  of  Schone 
claims  decided  preference  on  account  of  the  con- 
cordant results  obtained  and  easy  manipulation.  It 
is  represented  by  Fig.  4.  The  main  part  is  the 
agitator-funnel,  the  cylindrical  portion  of  which,  BC, 
the  true  suspension -chamber,  is  maintained  in  the 
exact  proportion  represented.  The  diameter  of  the 
lower  part,  D,  must  not  be  more  than  5  mm.  nor  less 
than  4  mm.  in  width.  The  same  dimensions  must 
be  preserved  in  the  bend,  DEF,  and  in  the  lower 
part  of  the  tube,  EG.  The  latter  may  be  widened, 
but  not  narrowed,  above.  The  exit-tube,  HJKL,  is 
made  of  barometer-tubing,  the  inner  diameter  of 
which  should  equal  3  mm.  as  nearly  as  possible.  The 
angle  at/  should  be  between  40°  and  45°.  The 
exit-tube  is  so  arranged  at  the  deepest  point  on  the 
bend,  K,  that  the  passing  water-column  is  directed 
downward  a  little  obliquely.  It  should  be  round, 
and  should  possess  well-rounded  edges  and  a  diameter 
of  i^  mm.  The  arm,  KL,  is  somewhat  over  i^§ 
m.  long,  and  serves  to  measure  the  pressure  under  which  the  water 
issues  at  K.  It  is  provided  from  the  lowest  point  upward  with  a 
scale,  of  which  i-io  cm.  is  divided  in  mm.,  10-50  in  ^  cm.  divis- 
ions, and  the  remainder  in  whole  cm.  divisions.  The  entrance- 


FIG.  4. 


44  CHEMICAL-TECHNICAL    ANALYSIS. 

tube,  G,  is  connected,  by  means  of  a  conduit,  with  a  water-reser- 
voir, which,  with  25  1.  contents,  should  be  at  the  most  10  cm.  high. 
A  stopcock  placed  in  the  circuit  regulates  the  flow.  By  means  of 
a  cock  an  upright  tube,  bent  perpendicular,  is  inserted  in  the  water- 
tank.  This  permits  an  entrance  of  air  during  the  flow  from  the 
enclosed  space  and  acts  as  a  level-indicator  when  refilling. 

With  funnel  and  exit-tubes  of  the  above  dimensions  the  velocity 
in  the  suspension-chamber  may  be  varied  between  0.2—4  mm.  per 
second.  Before  using  the  apparatus  the  relation  between  this  ve- 
locity and  the  height  of  the  water  in  the  pressure-indicator  (piezo- 
meter) must  be  determined.  The  velocity  is  equal  to  the  issue  in 
one  second  divided  by  squares  of  the  cross-section  of  the  suspension- 
chamber.  To  determine  the  latter  a  mark  is  made  above  C,  and 
the  water  is  allowed  to  enter  up  to  that  point. 

Fifty  c.c.  water  are  then  added  from  a  pipette,  and  the  difference 
in  level  in  the  suspension-chamber  read  off  by  means  of  a  rule  or 
cathetometer.  This  height  divided  into  the  50  c.c.  added  gives 
the  area  of  the  average  cross -section  of  the  suspension -chamber. 
The  "  piezometer  "  levels  corresponding  to  a  velocity  of  .2,  .5  and 
2  mm.  are  measured  and  recorded  for  the  subsequent  determinations. 
50  grs.  of  the  clay  selected  and  dried  at  ioo°-i2o°  are  softened  in 
water  and  boiled  briskly  at  least  ^  hour,  with  addition  of  a  few  c.c. 
caustic  soda.* 

When  the  clay  has  become  thoroughly  disintegrated,  the  pasty 
mass  is  run  through  a  sieve  of  900  meshes.  With  the  aid  of  a  soft 
brush  and  agitation  any  grains  of  sand  greater  than  .2  mm.,  as  well 
as  pebbles,  roots,  etc.,  are  separated.  That  which  has  passed 
through  the  sieve  and  the  washings  from  the  sand  are  placed  in  a 
beaker  and  allowed  to  settle,  after  which  the  clear  liquid  is  poured 
off  and  the  settlings  are  washed  into  the  agitator  funnel.  Sufficient 
water  only  to  raise  the  level  in  the  suspension-chamber  to  C  is 
used,  and  simultaneously  the  stopcock  is  opened  slightly  and  water 
is  admitted  to  prevent  clogging  in  the  base  of  the  funnel.  There- 
upon water  is  slowly  allowed  to  ascend  the  funnel,  so  that  the 

*  Clays  containing  lime  are  treated,  in  addition,  with  cold  concentrated  hydro- 
chloric acid  in  order  to  remove  the  carbonates  which  frequently  cement  particles 
together.  After  carbonic  acid  evolution  has  ceased,  the  acid  is  completely  washed 
out. 


ANALYSIS    BY    MECHANICAL    MEANS.  45 

volume  at  10  cm.  is  completely  filled  in  500  seconds.  The  exit- 
tube  is  then  adjusted  and  regulated  to  maintain  an  influx  of  a 
velocity  equivalent  to  .2  mm.  in  the  piezometer.  As  soon  as 
the  receiving  beaker-glass  receives  clear  liquid,  i.e.  the  water  in 
the  chamber  clarifies,  the  particles  operated  upon  by  a  current  of 
this  velocity  have  been  removed.  The  receiver  is  then  removed 
and  the  piezometer  regulated  for  a  velocity  of  .5  mm.  Veloci- 
ties under  .5  mm.  require  an  influx  of  about  3  liters,  and  a 
greater  velocity  requires  4-5  liters.  The  liquids  in  the  receivers 
are  allowed  to  clarify  completely,  and  the  supernatant  liquid  is 
drawn  off  with  a  siphon.  The  residue  is  washed  into  a  porce- 
lain dish,  dried  and  weighed.  The  residue  in  the  funnel  is  like- 
wise emptied  into  a  porcelain  dish  by  inverting  the  apparatus 
over  the  dish  and  forcing  through  it  a  brisk  current  of  water. 
The  quantity  is  determined  by  siphoning,  drying  and  weighing. 
The  finest  removable  particles  which  take  time  to  settle  are  de- 
termined by  difference.  Coarse  sand  remaining  on  the  sieve  is 
also  weighed.  The  products  obtained  are  designated  as  follows : 

(a]  Fine  clay,  (Size)  .oi  mm.-  Current  velocity,   .2  mm. 

(6)  "  Schluff "  clay,      "      .01    "    -.02  mm.  "  "         .5     " 

(t)  Dust,  "        .02      "     -.05       «  "  «         2.          " 

(of)  Fine  sand,  "      .05    "    -  .2     "  Residue  in  the  funnel. 

(<?)  Coarse  sand,  "       above        .2     "  Residue  in  the  sieve. 

Pyrometric  Tests. 

The  behavior  of  clay  at  high  temperatures  is  of  vast  import- 
ance in  determining  the  shrinkage,  the  color,  the  appearance  of 
flaws,  as  well  as  the  refractoriness.  To  study  this  behavior 
pyrometers  are  necessary,  in  the  first  place,  to  measure  the  tem- 
perature obtained.  For  this  purpose  sheets  of  pure  silver,  pure 
gold,  and  alloys  of  the  same  containing  20  per  cent,  and  upward 
of  gold,  besides  gold-platinum  alloys,  are  used,  from  which  the 
following  scale  has  been  prepared  : 

Pure  silver.  Melting-point,  960°  C. 

Alloy,             80  pts.  silver.           20  pts.  gold.  "  "  •  983°  C. 

"                 60    "      "                40    "     "  "  '*  1006°  C. 

«                 40    "      "                60    "     "  "  "  1029°  C. 

"                 20    "      "                80    "     "  "  "  1052°  C. 

Pure  gold.  "  "  1075°  C. 

"                 95    "gold.             5  pK  platinum.  "  "  Hio°C. 

«                 90    "     "                 10    "        "  "  "  1145°  C. 


46  CHEMICAL-TECHNICAL    ANALYSIS. 

For  higher  temperatures,  where  alloys  of  gold  and  platinum  are 
no  longer  suitable,  Seger  has  introduced  another  form  of  pyro- 
scope. 

This  consists  of  a  series  of  porcelain  glazes  containing  increas- 
ing amounts  of  alumina  and  silica,  and  which  possess  an  increas- 
ing melting-point. 

These  substances  are  shaped  in  the  form  of  a  tetrahedron — "  Se- 
ger's  cones."  To  measure  the  temperature  these  are  placed  in  the 
experimental  or  in  the  large  furnace.  As  soon  as  the  point  of  a  cone 
is  inclined  in  such  a  manner  as  to  touch  the  plate  upon  which  it  is 
placed  it  has  reached  a  corresponding  temperature. 

Thirty -six  such  cones  were  made  and  designated  with  increasing 
numbers  in  such  a  way  that  the  melting-point  of  No.  i  corresponded 
to  1150°  (approximately  that  of  alloy  of  90  parts  gold  and  10 
parts  platinum),  while  No.  20  represented  a  temperature  of  1700°. 
Assuming  now  that  the  differences  in  temperature  are  equal  to  one 
another,  then  every  subsequent  number  corresponds  to  an  increase 
of  29°.  For  example,  No.  30  corresponds  to  2000°  C.  The 
compositions  of  these  cones  are  given  by  Seger,  and  they  can  be 
obtained  through  the  "  Laboratorium  fur  Thonindustrie  in  Berlin.* 

For  lower  temperatures  easily -fusible  cones  have  also  been  pre- 
pared to  replace  the  expensive  alloys.  They  range  from  No.  .  i 
(960°  C.),  .9,  etc.,  to  i.  (1131°  C.),  making  in  all  a  total  of  46. 

The  numbers  corresponding  to  the  temperature  required  for  dif- 
ferent wares  are : 

Bricks,  tiles,  terra-cotta,  etc.,  ......  to    5 

Earthenware,  unglazed, from    3  "  lo 

"           glazed, "I 

Stoneware,      .........  from    5   "  10 

Refractory  products,  fire-brick,          .         .         .         .          .  "     10  "  20 

Porcelain, "     15   "  20 

(0)  Tests  for  shrinkage,  color  and  flaws. 

A  stiff  paste  is  made  of  the  clay  with  about  twenty  times  its 
weight  of  water,  and  this  is  rolled  into  a  form  of  about  8  cm. 
length,  4  cm.  width  and  i  cm.  thickness. 

*  The  temperatures  represented  by  each  are  to  be  found  in  an  accompanying 
explanation. 


ANALYSIS  BY  MECHANICAL  MEANS. 


47 


On  removing  the  models  so  prepared  from  the  moulds  they  are 
provided  by  means  of  a  needle-point  with  a  longitudinal  and  two 
perpendicular  lateral  marks,  the  distance  between  which  is  measured 
by  means  of  a  rule  provided  with  a  vernier.  The  forms  are  allowed 
to  dry  on  a  wire  gauze,  after  which  the  distance  between  marks  is 
again  measured.  The  shrinkage  by  drying  is  so  obtained.  They 
are  then  ignited  with  steadily  increasing  temperature  in  a  muffle  or 
furnace  similar  to  the  Deville  blast-furnace,  described  later,  until 
baked,  during  which  time  the  temperatures  are  measured  by  means 
of  test-cones.  The  tints,  the  formation  and  fusion  of  flaws  corres- 
ponding to  different  temperatures,  and,  further,  the  shrinkage,  are 
determined.  An  idea  of  the  porosity  can  also  be  formed  by  making 
an  ink-streak,  and  observing  whether  the  ink  is  absorbed  or  whether 
a  sharply-defined  line  remains. 

(£)  Determination  of  refractoriness.     This  is  generally  conducted 
to  ascertain  the  melting-point  of  a  clay, 
or,  moreover,  if  the  clay  is  to  be  desig- 
nated as  infusible. 

The  latter  is  taken  into  account  first  of 
all,  although  it  may  be  stated  that  the 
determination  of  fusibility  is  similarly 
conducted. 

The  test  of  refractoriness  is  made  in 
the  Deville  blast-furnace,  Fig.  5.  This 
consists  of  the  hollow  cylinder,  A,  made 
of  refractive  material,  surrounded  below 
by  a  stout  wrought -iron  plate.  This 
plate  has  in  its  centre  an  opening  of  3 
cm.  diameter,  which,  in  turn,  is  sur- 
rounded by  two  rows  of  small  openings 
of  6  mm.  diameter  at  equal  distances 
from  one  another.  The  refractory  cylin- 
der, 35  cm.  high,  is  surrounded  by  an  iron  jacket,  which  is  raised  8 
cm.  above  the  perforated  plate,  and  which  rests  on  an  iron  plate  sup- 
ported by  a  tripod.  The  space  between  plate  and  base  is  provided 
with  a  side-opening,  C,  of  25  mm.  width,  through  which  air  under 
pressure  is  conducted  from  a  cylindrical  bellows  50  cm.  in  diameter. 
The  upturned  rim  of  the  plate  above  is  sealed  with  a  sandy  non-shrink- 


FIG  5. — Deville  Oven. 


48  CHEMICAL-TECHNICAL    ANALYSIS. 

ing  clay  to  prevent  escape  of  air.  The  combustion-chamber,  D,  is 
slightly  conical,  having  9  cm.  diameter  below  and  n  cm.  above. 
The  strongly-refractory  material,  about  6  cm.  thick,  which  forms 
the  cylinder  consists  of  about  10  cm.  calcined  magnesite.  The 
upper  portion  is  filled  in  with  a  mixture  of  90  parts  calcined  mag- 
nesite and  10  parts  good  kaolin. 

The  clay  to  be  examined  is  moulded  into  forms  similar  to  those 
of  "  Seger' s  cones,"  and  these  are  enclosed  in  crucibles.  These 
crucibles  are  made  out  of  strongly-ignited  chamotte,  consisting  of 
equal  parts  alumina  and  fine  kaolin,  which  is  then  made  plastic  by 
means  of  best  quality  kaolin.  For  the  sake  of  cheapness,  the  sup- 
ports are  made  of  refractory  chamotte,  which  does  not  melt  below 
the  "Seger  cone"  No.  36. 

Manipulation. — The  material  under  examination  is  made  into 
small,  three-sided  pyramids  of  about  i  cm.  base  and  2  cm.  height 
and  then  dried.  Should  organic  matter  be  present,  the  models  are 
ignited  for  a  time  at  a  low  red  heat.  One  or  two  of  these  pyra- 
mids are  placed  simultaneously  with  the  corresponding  Seger  model 
into  the  crucible.  Model  No.  26  represents  in  pottery  industry  the 
fusibility  of  those  clays  which,  considered  as  refractory  materials, 
possess  the  lowest  melting-point.  The  crucibles  are  50  mm.  in 
height,  external  diameter  of  45  mm.  and  possess  walls  5  mm. 
thick.  The  lid  is  5  mm.  thick,  and  the  support  is  45  mm.  in 
diameter  and  50  mm.  high.  A  layer  7  mm.  in  height,  of  a  mixture 
consisting  of  fine,  sifted,  best  quality  and  previously  suspended 
Zettlitz  kaolin  and  alumina  is  poured  in  the  crucible  and  com- 
pressed. On  this  layer  samples  and  ' '  Seger  cones  ' '  are  alternately 
placed  in  a  circle.  By  lightly  pressing  down  on  them  they  attain 
the  necessary  hold.  With  a  pair  of  long-armed  iron  tongs  the 
support  is  placed  over  the  large  hole  in  the  bottom  plate  ;  the 
covered  crucibles  are  placed  upon  it  and  heating  is  begun.  Firing 
is  begun  by  igniting  about  30  grams  compressed  paper  and  throwing 
it  into  the  furnace -chamber.  The  bellows  should  not  be  com- 
pressed too  rapidly,  but  about  25  times  a  minute.  About  200 
grams  of  charcoal,  hazel-nut  size,  are  placed  on  top  of  the 
paper.  During  this  operation  the  paper  ash  is  withdrawn  from  the 
furnace.  When  the  charcoal  becomes  ignited  a  weighed  quantity 
of  broken  retort  graphite  is  thrown  in.  The  pieces  should  be  about 


ANALYSIS    BY    MECHANICAL    MEANS.  49 

hazel-nut  size,  and  300  pieces  should  weigh  about  i  kg.  The 
compression  of  the  bellows  is  increased  to  about  50  times  per 
minute,  and  is  continued  until  the  crucible  comes  plainly  into  view. 
.  9-1  kg.,  usually  started  with,  suffice,  when  consumed,  to  have  melted 
model  26.  In  order  to  attain  higher  temperature  the  amount  of 
fuel  with  each  experiment  is  varied  from  26-40  grams.  The 
exact  amount  of  fuel  is  not  capable  of  being  determined.  It  de- 
pends on  the  heating-power  of  the  graphite,  which,  however,  after 
several  experiments,  can  be  learned.  During  the  firing  the  furnace 
is  covered  with  a  lid.  The  crucibles  are  broken  open  on  cooling. 
Since  the  gases  in  the  furnace,  depending  on  whether  they  possess 
oxidizing  or  reducing  power,  exert  a  great  influence  on  the  appear- 
ance of  the  clay,  and  since,  in  addition,  the  determination  depends 
largely  on  the  subjective  judgment  of  the  manipulator,  therefore, 
without  taking  into  account  the  behavior  at  lower  temperatures, 
only  the  actual  melting-point  in  Seger's  temperature-units  will  be 
given. 

(c)   Calculation  of  refractoriness  from  the  analysis  : 
The  exact  analysis  of  a  clay  is  also  capable  of  giving  an  insight 
into  the  degree  of  refractoriness. 

As  a  standard  for  this  the  quotient  of  refractoriness  is  deter- 
mined. This  is  done  by  determining  the  ratio  of  fluxing  material 
to  alumina  on  the  one  hand,  and  that  of  alumina  to  silica  on  the 
other,  and  then  deriving  the  corresponding  oxygen.  Iron  oxide  is 
calculated  in  the  form  of  ferrous  oxide.  Let  a  represent  the  oxy- 
gen in  the  alumina,  b  that  in  silica,  and  c  that  in  the  fluxing  material 
(ferrous  oxide,  lime,  magnesia,  potassium  oxide).  Then  the  above 

a  b 

ratios  become  --=.A  and  --=iB.       The  quotient  of    refractoriness 
c  a 

T> 

(^)  then  equals  — .       A  clay  is  still  considered  refractory  when 

-/TL 

this  value  lies  between  3  and  4.  The  more  refractory,  the  more 
these  values  are  exceeded  ;  the  less  refractory,  the  lower  the  values 
sink  below  these  limits. 

Example  :  The  Zettlitzer  kaolin,  considered  very  refractory,  and 
which  possesses  the  following  composition,  gives  the  adjoining 
oxygen  values  : 

4 


50 


CHEMICAL-TECHNICAL    ANALYSIS. 


Constituents. 

Oxides. 
Per  Cent. 

Oxygen. 
Per  Cent. 

Silica  

45.68 

24.36  (b) 

Alumina  

78.154 

18.03  (a) 

.08 

.02  1 

Ferric  oxide 

GO 

18         ,  ,  . 

Magnesium  oxide      .... 

38 

;I5  h^(c) 

Potassium  oxide  

66 

.11  1 

Loss  on  ignition   

I  7  OO 

The  comparison  of  the  fluxes  with  alumina  taken  as  unity  yields 

— '— -:rr39.i3  (A}.     Alumina  compared  with  silica  taken  as  unity 
.46 


15.03 

Accordingly,  the  formula  of  the  clay  would  be  39.19  (A12  Os.i.35 
SiO2)  -j-  RO,  and  the  quotient  of  refractoriness  F=  -  z= 
28,98. 


III.  Metallurgical  Industry. 


1.  Iron. 

THE  following  determinations  are  made,  as  a  rule,  for  the  various 
kinds  of  iron  (pig  iron,  wrought-iron,  etc.)  :  silicon,  carbon,  man- 
ganese, phosphorus,  sulphur.  Concerning  sampling,  let  it  be  stated 
that  wrought-iron  and  gray  pig-iron  can  be  obtained  in  desired  form 
by  boring,  planing  or  turning,  whereas  white  pig-iron  and  hardened 
steel  can  be  broken  up  with  a  hammer  and  subsequently  divided  in 
a  steel  mortar. 

(#)  Silicon.  Following  the  method  of  Brown,  1—2  grs.  iron — 
of  white  pig-iron  and  steel  a  larger  quantity — are  heated  with  nitric 
acid  (sp.  gr.  1.2)  until  everything  has  dissolved.  35—40  c.c.  sul- 
phuric acid  (1:4)  are  then  added,  and  the  whole  is  heated  on  a 
sand-  or  water-bath  until  the  nitric  acid  has  volatilized.  To  the 
chilled  liquid  40-50  c.c.  water  are  then  carefully  added,  after 
which  it  is  heated  to  complete  solution  of  iron  salts  and  is  filtered 
hot.  The  residue  is  washed  first  with  hot  water  until  iron  is  no 
longer  detectible,  and  then  with  hot  hydrochloric  acid  (sp.gr.  1.12) 
about  four  times,  and  finally  with  hot  water  to  completely  remove 
the  hydrochloric  acid.  The  moist  filter  is  consumed  in  a  platinum 
crucible  at  a  low  temperature  and  then  ignited  until  the  silica  has 
become  white,  a  point  which  with  graphitic  pig-iron  is  often  not 
reached  for  2-3  hours.  Should  the  silica  contain  iron,  it  is  fused 
with  sodium-potassium  carbonate. 

(£)  Carbon.  Total  carbon  and  graphite  are  usually  determined, 
and  bound  carbon  is  calculated  by  difference. 

(a)  Total  carbon.  The  iron  is  dissolved  in  neutral  cupro-ammo- 
nium  chloride  solution,  which  is  prepared  by  dissolving  300  grs. 
neutral  cupro-ammonium  chloride  in  one  liter  water  or  340  grs. 
crystallized  copper  chloride  and  214  grs.  ammonium  chloride  in 
1850  c.c.  water.  In  the  residue  the  carbon  is  determined  as  car- 
bonic acid  by  combustion. 


52  CHEMICAL-TECHNICAL    ANALYSIS. 

Procedure. — i  gr.  pig-iron,  3-5  grs.  steel  or  5—10  grs.  wrought- 
iron  in  pulverized  condition  are  placed  in  an  Erlenmeyer  flask,  and 
50  c.c.  of  the  above  solution  are  added  for  every  gram  of  iron. 

The  solution  is  briskly  agitated  at  first  at  ordinary  temperature, 
later  at  a  temperature  of  40°  to  50°.  The  iron  dissolves  rapidly 
with  separation  of  copper,  which  later  dissolves  likewise,  leaving  a 
residue  consisting  solely  of  carbon,  silicide-,  phosphide-  and  sulphide 
of  iron.  Should  a  precipitate  of  basic  salts  of  iron  form,  several 
drops  of  hydrochloric  acid  are  added  to  the  solution.  It  is  then 
filtered  on  an  asbestos  filter  and  subsequently  on  a  filter  pump. 
The  first  portions  of  the  filtrate  are  tested  for  carbon,  which  may 
have  passed  through,  by  dilution  with  hydrochloric  acid  and  water 
until  transparent.  It  is  then  washed  first  with  cupro-ammonium 
chloride,  and  later  with  hot  water  until  chlorine  is  no  longer  de- 
tectible,  then  with  alcohol,  finally  with  ether ;  whereupon  the  pre- 
cipitate is  dried  at  a  low  temperature.  The  carbon  on  the  asbestos 
filter  is  oxidized  to  carbonic  acid  by  treatment  with  chromic  acid 
and  sulphuric  acid.  To  determine  the  carbonic  acid,  apparatus  for 
absorption  of  the  latter  is  used,  special  care  being  taken  to  dry  the 
evolving  ga-es  with  pumice-stone,  sulphuric  acid  and  calcium 
chloride.  In  the  generator  of  the  apparatus  is  placed  the  carbon 
deposit,  together  with  the  asbestos-tube,  which  has  been  carefully  cut 
with  a  file.  40  c.c.  concentrated  sulphuric  acid  are  added,  fol- 
lowed, when  cool,  by  8  grs.  crystallized  chromic  acid.  The  flask 
is  then  attached  to  the  apparatus  and  gently  warmed.  The  gases 
evolved  first  pass  through  an  upright  condenser,  then  through  the 
drying  apparatus,  and  finally  into  the  absorption  vessels,  which 
consist  of  two  tubes  containing  soda-lime.  The  second  vessel, 
however,  is  also  filled  about  y$  its  capacity  with  calcium  chloride. 
In  addition,  a  protecting  tube  filled  with  calcium  chloride  is  at- 
tached. Heating  is  continued  until  evolution  has  ceased  and 
sulphuric  anhydride  fumes  appear  in  the  condenser.  An  aspirator 
is  then  attached,  and  air,  freed  from  carbonic  acid,  is  drawn  through 
the  system  for  some  time.  The  soda-lime  tubes  are  then  detached 
and  weighed. 

Recently  methods  have  been  proposed  to  determine  the  carbon 
volumetrically.  That  of  Lunge  and  Marchlewski  is  particularly 
suited  to  this  purpose.  According  to  the  latter,  .5-5  grs.  of  the 


IRON.  53 

iron  under  investigation  are  repeatedly  agitated  in  a  flask  with  a 
saturated  copper  sulphate  solution  for  1-6  hours.  The  flask  is  then 
connected  with  a  condenser  and  a  suitable  gasometer  and  warmed 
with  the  quantity  of  chromic-sulphuric  acid  mixture  necessary  to 
insure  oxidation.  The  authors  have  constructed  for  this  purpose 
special  forms  of  generators  and  gas  burettes.  An  exact  description 
of  these  would  lead  too  far.  They  may  be  found  in  the  Zeitschrift 
fiir  angewandte  Chemie,  Jahrgang  1891,  S.  412.  The  apparatus  is 
obtainable  from  J.  G.  Cramer,  in  Zurich,  C.  Desaga,  in  Heidel- 
berg, and  others. 

(/?)  Graphite.  4-5  grs.  iron  are  dissolved  by  warming  with  dilute 
hydrochloric  acid.  The  residue  is  filtered  on  an  asbestos  bed.  The 
latter  is  washed  with  hot  water  until  the  filtrate,  on  addition  of 
silver  nitrate,  no  longer  opalesces.  It  is  then  washed  4-5  times 
with  dilute  caustic  potash,  followed  by  alcohol,  to  remove  potash, 
and  finally  with  ether.  After  drying,  the  graphite  is  oxidized  like 
the  total  carbon  with  chromic  acid  and  sulphuric  acid. 

(<:)  Manganese.  Of  the  many  methods  proposed  for  this  deter- 
mination, that  of  Volhard  only  will  be  described  here. 

Principle. — If  to  a  neutral  or  slightly  acid  solution  of  a  manga- 
nese salt,  permanganate  of  potash  be  added  at  80°  C.,  a  complete 
precipitation  of  the  manganese  ensues. 

The  equation  Mn2O7  -f  3MnO  =  5MnO2,  originally  proposed  for 
this  method,  is  incorrect  under  the  conditions  given,  according  to 
Volhard,  inasmuch  as  a  precipitate  containing  manganous  oxide, 
5  MnOa.  MnO  is  formed.  If,  however,  a  solution  of  a  zinc,  lime  or 
magnesium  salt  be  added,  a  peroxide  containing  zinc  oxide,  lime  or 
magnesia  will  be  precipitated. 

Observing  these  facts,  manganese  in  iron  may  be  determined  by 
adding  zinc  oxide  to  the  solution  containing  all  the  iron  in  the  ic 
and  all  manganese  in  the  ous  condition.  Ferric  oxide  is  precipi- 
tated, while  an  equivalent  amount  of  zinc  is  dissolved.  The  solu- 
tion is  then  titrated  with  permanganate  of  potash. 

Standardization. — The  permanganate  is  standardized  on  iron  in 
the  usual  manner,  and  is  then  calculated  into  manganese  units  (of 
manganous  oxide)  by  use  of  the  equation  ioFe(=  2KMnO4)=  3Mn. 

Experiment. — About  4  grs.  sample  (less,  if  it  contain  much 
manganese)  are  dissolved  in  nitric  acid  (sp.  gr.  1.2)  ;  the  solution 


54  CHEMICAL-TECHNICAL    ANALYSIS. 

is  evaporated  to  dryness,  and  the  residue  is  heated  for  about  i  hour 
on  a  sand-  or  air-bath.  Thereupon  it  is  dissolved  in  warm  hydro- 
chloric acid;  20  c.c.  sulphuric  acid  (i  :  i)  are  added,  and  the 
whole  is  heated  until  sulphuric  acid  volatilizes.  It  is  then  taken 
up  with  water  and  washed  into  a  500  c.c.  graduated  flask.  The 
excess  of  acid  is  nearly  neutralized  with  sodium  carbonate,  and, 
while  being  agitated,  freshly  calcined  zinc  oxide,  suspended  in 
water,  is  added  until  the  solution,  which  gradually  turns  dark  brown, 
suddenly  congeals  from  separation  of  the  entire  ferric  oxide.  Water 
is  then  filled  in  to  the  mark,  and  100  and  250  c.c.  respectively  of 
the  clear  filtrate  are  withdrawn  for  titration  with  permanganate, 
which  should  be  approximately  TO  normal. 

The  solution  to  be  titrated  is  heated  to  about  80°  C.  It  is  vig- 
orously shaken  while  the  permanganate  is  introduced  until  the  liquid 
above  the  flocculent  precipitate,  which  settles  rapidly,  is  of  a  pink 
color.  It  is  then  boiled,  and  when  the  color  has  disappeared,  more 
permanganate  is  added  until  a  permanent  color  remains. 

Modification  by  Ulzer  and Brull* — In  order  to  overcome  the  not 
inappreciable  difficulty  of  detecting  the  end  reaction  of  the  titration 
with  permanganate,  20  c.c.  of  a  .5  per  cent,  solution  of  hydrogen 
peroxide  may  be  added  to  the  above  solution,  which  has  been  freed 
from  ferric  oxide  by  means  of  zinc  oxide  and  filtered. 

This  is  followed  by  the  addition  of  caustic  soda  as  long  as  a  pre- 
cipitate forms,  after  which  it  is  boiled.  Manganese  is  precipitated 
as  5MnOrMnO.  Upon  cooling,  oxalic  acid  of  known  strength  is 
added,  together  with  pure  dilute  nitric  acid.  It  is  then  digested  at 
a  low  heat  until  the  precipitate  redissolves,  after  which  it  is  heated 
almost  to  boiling,  and  the  excess  of  oxalic  acid  is  titrated  with 
permanganate. 

(</)  Phosphorus.  To  1-5  grs.  iron  nitric  acid  (sp.  gr.  1.2)  is 
added,  and  heat  is  applied  to  dissolve  it  finally.  Then  to  fully 
oxidize  the  phosphorus  it  is  boiled  with  25  c.c.  of  a  i  per  cent, 
potassium  permanganate  solution.  An  aqueous  solution  of  8-10 
grs.  ammonium  chloride 'is  added  to  dissolve  the  manganese  perox- 
ide formed. 

The  solution,   clarified  by  reheating,  is  evaporated  to   dryness, 

*•  Contribution  of  the  K.  K.  Technol.  Gen.  Mus.,  Jahrg.  1895,  p.  312. 


IRON. 


55 


and  the  residue  dissolved  by  treating  with  10-20  c.c.  concentrated 
hydrochloric  acid.  The  solution  is  evaporated  to  syrupy  consist- 
ency and  10  c.c.  nitric  acid  are  added,  followed,  after  a  few 
moments,  by  hot  water.  It  is  then  filtered,  washed  with  water 
containing  nitric  acid,  nearly  neutralized  with  ammonia,  though  the 
liquid  is  kept  clear.  The  solution,  now  about  100  c.c.,  is  heated 
to  70°,  and  precipitated  with  25  c.c.  molybdate  solution.  After 


FIG.  6. — Apparatus  for  Determining  Sulphur. — Johnston  and  Landolt. 

standing  for  two  hours  at  a  temperature  of  40°  C.  the  liquid  is 
filtered  off  and  the  precipitate  is  washed  with  dilute  molybdate 
solution,  containing  nitric  acid,  as  long  as  iron  is  present.  It  is 
then  dissolved  in  ammonia,  and  precipitated  with  magnesia  mixture 
in  the  usual  manner. 

(*)  Sulphur.  Using  the  less  recent  directions  of  Johnston  and 
Landolt,  5  grs.  finely-divided  iron  are  introduced  into  the  flask,  A, 
of  the  accompanying  apparatus  (Fig.  6).  Bromine-hydrochloric 


56  CHEMICAL-TECHNICAL    ANALYSIS. 

acid  mixture  is  allowed  to  flow  from  b  into  the  tube,  C,*  which  is 
filled  with  glass  beads.  The  stopcock,  g,  is  closed  during  the 
above  operation.  5-10  c.c.  concentrated  hydrochloric  acid  are 
run  into  the  flask  from  the  funnel,  c.  The  hydrogen  sulphide  gen- 
erated is  oxidized  by  the  bromine  to  sulphuric  acid.  When  the 
bromine-hydrochloric  acid  mixture  decolorizes,  it  is  run  into  the 
flask  beneath,  and  is  replaced  by  fresh  solution.  When  the  evolu- 
tion of  gas  in  A  ceases,  more  hydrochloric  acid  from  C  is  added, 
and  the  flask  finally  heated,  while  carbonic  acid  is  run  through, 
which  has  been  washed  with  an  interposed  wash-bottle  containing 
mercuric  chloride,  to  absorb  any  hydrogen  sulphide. 

After  having  been  brought  to  boiling,  the  bromine  solution  is 
allowed  to  flow  into  the  flask,  the  glass  beads  are  washed  with 
water,  and  the  solution  is  evaporated  in  a  porcelain  dish.  After 
the  bromine  and  the  excess  of  hydrochloric  acid  have  volatilized, 
the  liquid  is  diluted  with  water,  filtered,  and  the  sulphuric  acid  is 
precipitated  with  barium  chloride.  Bromine  and  hydrochloric  acid 
must,  of  course,  previously  be  tested  for  sulphuric  acid.  Instead  of 
the  disagreeable  bromine-acid  mixture,  an  ammoniacal  hydrogen  per- 
oxide solution,  entirely  free  from  sulphuric  acid,  may  be  used. 

According  to  the  new  and  popular  procedure  of  Schulte,f  10 
grams  granulated  sample  are  placed  in  the  flask,  A,  of  the  accom- 
panying apparatus  (Fig.  7).  The  receiver,  ft  contains  45—50  c.c. 
of  a  mixture  of  25  grs.  cadmium  acetate  and  200  c.c.  glacial  acetic 
acid  diluted  to  i  liter.  Another  portion  of  10  c.c.  of  this  solution 
is  placed  in  the  cylindrical  vessel,  H.  The  apparatus  is  then  ar- 
ranged as  seen  in  the  figure.  Thereupon,  200  c.c.  hydrochloric 
acid  (i  :  2)  are  placed  in  the  funnel,  JB,  and  allowed  to  slowly 
descend  into  the  flask,  A.  By  slowly  heating  the  flask,  the  iron  is 
brought  into  solution  in  about  i^-i^  hours.  It  is  now  boiled 
until  all  hydrogen  sulphide  has  been  driven  out  of  A,  which  will 
be  the  case  when,  after  1-2  minutes,  the  clatter,  due  to  steam  con- 
densation, is  heard  in  the  receiver.  The  hydrogen  sulphide  evolved 
produces  a  precipitate  of  cadmium  sulphide  in  f,  while  under  nor- 
mal conditions  no  hydrogen  sulphide  will  enter  H.  In  any  case, 

*  In  place  of  the  tube,  Winkler  absorption  coils,  containing  bromine  and  hydro- 
chloric acid,  may  be  advantageously  used, 
f  Stahl  u  Eisen,  Jahrg.  1896,  S.  865. 


ZINC    BLENDE. 


57 


the  stopper,  E,  is  raised,  and  a  quantity  of  5—7  c.c.  copper  sul- 
phate, containing  sulphuric  acid,  is  added.  This  is  prepared  by 
dissolving  80  grs.  crushed  copper  sulphate  in  750  c.c.  water.  175 
c.c.  concentrated  sulphuric  acid  are  added,  the  whole  is  diluted 
to  one  liter,  and  filtered.  Upon  the  addition  of  this  solution,  a 
rapid  and  complete  transformation  of  cadmium  sulphide  to  copper 
sulphide  takes  place.  This  may  be  hastened  by  agitation.  The 
separated  copper  sulphide  is  filtered  off  and  estimated  by  conversion 
into  oxide  or  subsulphide.  One  equivalent  of  sulphur  is  reckoned 


FIG.  7. — Apparatus  for  Determining  Sulphur. — Schulte. 

for  every  equivalent  of  copper  found.  Therefore  63.5  copper 
(=  79.5  copper  oxide  =  same  amount  of  cuprous  sulphide)  =  32 
sulphur. 

Should  a  small  precipitate  of  cadmium  sulphide  perhaps  appear 
in  Ht  the  two  liquids  are  united  and  simultaneously  precipitated 

with  copper  sulphate. 

2.  Zinc  Blende. 

The  most  important  determinations  in  this  are  sulphur,  zinc"  and 
lead.  The  following  methods,  used  in  most  zinc  works,  are  pre- 
ferable :* 

*  Lunge,  Taschenbuch  fur  Sodafabrikation,  etc. 


58  CHEMICAL-TECHNICAL    ANALYSIS. 

(a)  Total  sulphur.  .5  gr.  of  impalpable  sample  is  covered 
with  about  20  c.c.  of  a  mixture  of  3  parts  concentrated  nitric 
acid  and  i  part  concentrated  hydrochloric  acid,  or  else  with  a  sat- 
urated bromine-hydrochloric  acid  mixture,  and  allowed  to  stand 
over  night,  after  which  it  is  evaporated  almost  to  dryness  and  sev- 
eral c.c.  hydrochloric  acid  introduced,  followed  by  50  c.c.  hot 
water.  It  is  then  filtered  and  precipitated  with  barium  chloride. 

(^)  Zinc.  According  to  the  modified  Schaffner  process,  2.5  grs. 
finely-powdered  sample  are  treated  with  12  c.c.  fuming  nitric  acid 
in  an  Erlenmeyer  flask,  at  first  in  the  cold  and  finally  at  a  low  heat, 
until  the  red  fumes  have  disappeared,  20-25  c.c.  cone,  hydrochloric 
acid  are  added,  and  the  liquid  is  evaporated  to  dryness  on  a  sand- 
bath.  The  residue  is  taken  up  with  5  c.c.  hydrochloric  acid  and  a 
little  water  and  heated  to  dissolve  soluble  portions.  Then  50-60 
c.c.  water  are  added,  and  heat  is  applied  again  to  maintain  it  at 
6o°-7o°  C.  Everything  should  dissolve  but  gangue  and  separated 
sulphur.  A  brisk  current  of  hydrogen  sulphide  is  conducted  into 
the  solution,  accompanied  by  a  subsequent  gradual  addition  of  50- 
100  c.c.  cold  water  while  the  liquid  is  being  agitated,  in  order  to 
completely  precipitate  all  lead  and  cadmium.  Excessive  dilution 
and  too  prolonged  an  addition  of  hydrogen  sulphide  should  be 
avoided.  The  precipitate  is  filtered  and  washed  with  TOO  c.c.  water 
containing  hydrogen  sulphide  and  5  c.c.  hydrochloric  acid  until  a 
drop  of  the  filtrate  no  longer  shows  a  trace  of  zinc  when  treated 
with  ammonium  sulphide.  Filtrate  and  washings  are  boiled  to  re- 
move hydrogen  sulphide,  and  the  iron  is  oxidized  by  addition  of  5 
c.c.  cone,  nitric  acid  and  10  c.c.  hydrochloric  acid.  After  partially 
cooling,  the  liquid  is  poured  into  a  graduated  flask  of  500  c.c, 
capacity,  and  100  c.c.  ammonia  (sp.  gr.  .9-.9i)  and  10  c.c.  satur- 
ated ammonium  carbonate  solution  are  added.  In  the  meantime 
an  ammoniacal  zinc  solution  of  known  strength  is  prepared  by  dis- 
solving a  quantity  of  chemically  pure  zinc,  approximating  the 
amount  of  zinc  contained  in  the  ore,  in  a  flask  of  500  c.c.  capacity, 
by  the  addition  of  5  c.c.  nitric  acid  and  20  c.c.  hydrochloric  acid 
and  diluting  with  about  250  c.c.  water,  100  c.c.  ammonia,  and  10 
c.c.  of  the  above  ammonium  carbonate  solution  are  added  ;  the 
solution  is  agitated  and  allowed  to  stand.  In  the  presence  of  man- 
ganese an  addition  of  10  c.c.  hydrogen  peroxide  should  precede 


ZINC    DUST.  59 

that  of  ammonia.  After  thoroughly  cooling,  both  flasks  are  filled 
to  the  mark,  and  the  contents  of  the  one  containing  the  ore  are  fil- 
tered through  a  dry  ribbed  filter.  In  titrating  100  c.c.  of  each  so- 
lution, ore  and  standard  are  placed  in  thick-walled  cylinders  and  are 
diluted  with  200  c.c.  water.  For  titration  a  concentrated  solu- 
tion of  commercial  crystallized  sodium  sulphide  is  very  suitable. 
The  latter  is  dissolved  in  10-20  volumes  of  water,  and  should  rep- 
resent approximately  .005— .01  gr.  zinc  per  c.c.  This  solution  is 
run  alternately  from  two  adjoining  50  c.c.  burettes  into  the  solu- 
tions, and,  in  fact,  2-3  c.c.  less  than  required  at  first. 

Drops  of  the  stirred  liquids  are  then  placed  on  a  strip  of  sensitive 
lead-acetate  paper  with  a  thin  glass  rod.  After  15—20  seconds  the 
drops  are  washed  off,  the  addition  of  sodium  sulphide  solution  is 
continued,  and  the  tests  with  lead-acetate  paper  are  repeated  until 
after  an  equal  period  faint  but  distinct  tints  of  equal  intensity  appear. 
It  is  desirable  to  contrast  the  first  result,  usually  approximate,  with 
two  or  three  more.  At  any  rate,  the  end  reactions  in  both  cylinders 
must  be  uniform  in  both  vessels  and  the  readings  must  be  made 
within  .05  c.c. 

Let  the  amount  of  zinc  in  the  standard  solution  =  a,  the  number 
of  c.c.  sodium  sulphide  used  in  titrating  100  c.c.  standard  solution 
=  b,  and  the  number  used  in  titrating  100  c.c.  solution  containing 

40  ac 
ore  (=  .  5  gr.  ore)  =  c  ;  then  the  percentage  of  zinc  =  ^— — 

In  very  exact  determinations  a  quantity  of  ferric  chloride  cor- 
responding to  that  in  the  ore  solution  is  added  to  the  standard 
solution  to  compensate  for  a  possible  precipitation  of  zinc  by  the 
ferric  hydrate. 

(V)  Lead.  The  precipitated  sulphides  in  b  are,  if  necessary, 
digested  with  a  fairly  concentrated  solution  of  sodium  sulphide, 
diluted  and  filtered.  The  residue,  plus  filter-paper,  is  dissolved  in 
dilute  nitric  acid,  evaporated  with  an  excess  of  sulphuric  acid,  and 
the  lead  is  determined  as  lead  sulphate. 

3.  Zinc  Dust. 

The  following  method  of  Drewsen,  modified  by  Fraenkel,  deter- 
mines the  reducing  value  only,  and  therefore  small  quantities  of 
iron  and  cadmium  present  are  calculated  as  zinc.  The  method 


60  CHEMICAL-TECHNICAL    ANALYSIS. 

depends  on  the  fact  that  by  the  action  of  sulphuric  acid  on  zinc,  in 
the  presence  of  an  excess  of  bichromate  of  potash,  a  part  of  the 
chromic  acid  is  reduced  to  chromic  oxide.  The  unaltered  chromic 
acid  is  determined  iodometrically,  and  the  zinc  is  calculated  from 
the  difference.  A  ^  normal  potassium  bichromate  solution,  con- 
taining 24.58  grs.  of  the  pure  salt  in  a  liter,  and  a  y2  normal 
hyposulphite  solution  are  suitable.  The  latter  is  exactly  standard- 
ized on  the  former.  In  operating,  approximately  .5  gr.  zinc  dust 
is  placed  in  a  dry  flask  of  about  ^ -liter  capacity  provided  with  a 
stopper.  50  c.c.  bichromate  solution,  next  5  c.c.  dilute  sulphuric 
acid  (i  :  5),  are  added,  and  the  mixture  is  agitated.  After  about 
5  minutes  10  c.c.  more  sulphuric  acid  are  added,  and  the  whole  is 
shaken  for  10  minutes,  when  complete  solution  usually  ensues.  In 
order  to  estimate  the  chromic  acid  yet  present,  40  p.c.  iodide  of 
potassium  solution  (i  :  10)  are  added,  followed  by  additional  20 
c.c.  sulphuric  acid.  Separation  of  considerable  iodine  ensues. 
(2CrO3  =  61).  After  dilution  with  400-500  c.c.  water,  the  iodine 
is  titrated  with  hyposulphite.  To  determine  the  end  reaction  with 
precision,  hyposulphite  solution  is  added  to  the  brown  iodine  solu- 
tion until  the  latter  becomes  yellow-green  in  color.  Starch  paste 
is  added  at  this  point,  whereby  the  liquid  turns  deep  green.  By 
continued  careful  titration  the  color  changes  gradually  into  a  deep 
blue  until  finally  the  comparatively  light-green  chromic  salt  is 
obtained,  at  which  point  the  titration  is  complete.  With  a  little 
practice,  a  sharp  end  reaction  is  go  ten.  The  difference  between 
the  quantity  of  bichromate  solution  added  and  the  quantity  of 
hyposulphite  solution  used  in  back  titration  gives  the  chromic  acid 
reduced  by  the  zinc,  from  which  the  zinc  can  be  calculated. 

i  K2Cr2O7  =  6  I  =  3  Zn. 

4.   Crude  and  Refined  Copper. 

Great  stress  has  been  recently  laid  on  the  technical  examination 
of  the  chemical  composition  of  the  kinds  of  copper  named.  Certain 
specifications  in  this  direction  are  required  ;  for  example,  for  rail- 
road consignments.  In  consequence,  various  kinds  of  copper  are 
often  subject  to  quantitative  chemical  analysis.  The  analysis  offers 
considerable  difficulty  when  contaminations,  usually  present  in  small 


CRUDE    AND    REFINED    COPPER.  61 

amount,  are  present  in  quantity.  When  an  exact  total  analysis  is 
desired,*  the  very  reliable  method  of  Fresenius  seems  to  be  the 
simplest  one.  The  method  is  given  here,  with  a  few  slight  modifi- 
cations by  Fraenkel. 

The  foreign  elements  which  are  to  be  determined  are  :  Silver, 
lead,  arsenic,  antimony,  tin,  bismuth,  iron,  cobalt,  nickel,  zinc, 
sulphur,  phosphorus  and  oxygen.  The  determination  of  gold  may 
usually  be  neglected.  Copper  is  calculated  with  sufficient  accuracy 
by  difference. 

100  grs.  copper  turnings  or  shavings  are  taken  for  the  analysis, 
and,  after  separation  of  particles  of  iron  by  means  of  a  magnet,  are 
dissolved  in  nitric  acid  (sp.  gr.  1.2).  Solution  had  best  be  con- 
ducted in  a  beaker  of  about  i  liter  capacity.  The  acid  is  gradually 
added  and  warmed  toward  the  end,  to  effect  complete  solution.  It 
is  filtered,  after  dilution  with  water,  into  a  graduated  2-liter  flask, 
washed  with  hot  water,  and  the  flask  (^4),  not  yet  filled  to  the 
mark,  is  stood  aside. 

The  residue  is  washed  from  the  filter  into  a  porcelain  crucible 
and  evaporated  to  dryness  ;  the  filter  ash  is  added  and  fused  with 
a  mixture  of  soda  and  sulphur.  .The  chilled  fusion  is  lixiviated 
with  hot  water,  filtered  into  a  graduated  flask  of  200  c.  c.  capacity 
and  washed  with  water  to  which  some  sodium  sulphide  has  been 
added.  The  filtrate  (,#),  which  is  diluted  to  the  mark,  is  likewise 
corked  up  and  preserved.  The  residue  (C),  together  with  the  filter- 
paper,  is  warmed  with  nitric  acid  (i  :  i),  diluted  with  water,  fil- 
tered and  added  to  flask  (A),  which  is  then  filled  to  the  mark. 
From  the  contents  of  this  flask  1000  c.c.  are  removed  for  the  deter- 
mination of  silver,  lead,  bismuth,  arsenic,  tin,  antimony,  iron, 
nickel,  cobalt  and  zinc,  and  the  remaining  liquid  is  preserved. 
This  1000  c.c.  represents  one-half  the  original  amount  of  substance 
taken.  It  is  placed  in  a  beaker,  about  4  drops  cone,  hydrochloric 
acid  are  added,  and  warmed  and  stirred,  in  case  turbidity  ensues, 
until  the  liquid  clarifies.  The  separated  silver  chloride  is  filtered 
off  and  washed.  The  silver  is  determined  as  usual.  The  lead  is 
determined  by  adding  85  grs.  cone,  sulphuric  acid  to  the  filtrate, 

*  For  the  simple  estimation  of  the  copper,  the  electrolytic  method,  by  all  means, 
answers  the  purpose  best. 


62  CHEMICAL-TECHNICAL    ANALYSIS. 

evaporating  on  a  water-bath  until  nitric  acid  is  completely  expelled, 
dissolving  the  separated  sulphate  of  copper  in  water  by  warming, 
and  filtering  off  the  insoluble  sulphate  of  lead.  The  latter  is 
washed  first  with  water  containing  sulphuric  acid,  and  then  over  a 
separate  receiver  with  dilute  alcohol.  The  lead  is  then  determined 
in  the  usual  manner. 

The  filtrate  from  the  lead  sulphate  is  heated  and  then  placed  in 
a  previously  weighed  flask  (Z>)  of  about  5  liters  capacity.  Suffi- 
cient hot  water  is  added  to  bring  the  total  volume  to  3—4  liters. 
About  50  c.c.  cone,  hydrochloric  acid  are  added,  and  a  brisk  con- 
tinuous current  of  hydrogen  sulphide  is  conducted  in,  until  com- 
plete precipitation  is  indicated  by  the  rapid  settling  of  the  precipi- 
tate and  a  perfectly  colorless  supernatant  liquid.  The  precipitate 
(£~)  contains  all  the  copper,  bismuth,  arsenic,  antimony  and  tin. 
Iron,  nickel,  cobalt  and  zinc  remain  in  solution.  Flask,  solution 
and  precipitate  are  weighed ;  the  weight  of  the  flask  is  deducted 
and  the  weight  of  liquid  and  precipitate  thereby  ascertained.  The 
weight  of  precipitate  is  found  by  calculating  the  copper  contained 
therein  into  copper  sulphide.  If  this  be  deducted  also,  the  weight 
of  liquid  alone  is  obtained.  As  soon  as  the  precipitate  has  well 
settled,  as  much  of  the  clear  liquid  as  possible  is  drawn  off  with  a 
siphon.  If  the  remaining  liquid,  precipitate  and  flask  be  now 
weighed  together,  the  difference  between  it  and  the  former  weight 
gives  the  weight  of  liquid  siphoned  off.  By  simple  proportion  the 
corresponding  quantity  of  original  substance  contained  therein  can 
be  calculated.  This  solution,  filtered  if  necessary,  serves  for  the 
determination  of  iron,  nickel,  cobalt  and  zinc.  For  this  purpose  it 
is  evaporated  as  far  as  possible  in  a  porcelain  dish  on  a  water-bath 
and  the  excess  of  sulphuric  acid  is  volatilized  over  a  naked  flame. 
The  residue  is  heated  with  water  and  nitric  acid,  filtered,  treated 
with  an  excess  of  ammonia,  and  the  precipitate  formed  is  dissolved 
in  hydrochloric  acid  and  reprecipitated  with  ammonia.  The  opera- 
tion is  repeated  if  necessary,  and  the  precipitate  is  finally  weighed 
as  ferric  oxide.  To  the  collected  filtrates  more  ammonia  is  added, 
followed  by  acetic  acid  to  slight  acid  reaction.  Hydrogen  sulphide 
is  conducted  into  the  heated  solution,  whereby  cobalt,  nickel  and 
zinc  are  precipitated.  These  are  filtered  off,  dried,  removed  as  far 
as  possible  from  the  filter,  and  dissolved  in  nitric  acid  and  a  little 


CRUDE    AND    11EFINED    COPPER.  63 

hydrochloric  acid.  The  filter  ash  is  added,  the  liquid  is  evaporated 
on  a  water-bath,  taken  up  with  water  and  a  little  hydrochloric  acid, 
and  then  exactly  neutralized  with  sodium  carbonate,  using  methyl- 
orange  as  indicator.  A  slow  current  of  hydrogen  sulphide  is  now 
led  in  for  a  brief  period.  A  few  drops  of  dilute,  preferably  very 
weak,  alkaline  sodium  acetate  solution  are  added,  whereby  an  ap- 
preciable darkening  of  the  precipitate  should  not  ensue.  A  very 
slow  current  of  hydrogen  sulphide  is  again  led  in  for  a  few  minutes, 
and  the  zinc  sulphide  formed  is  allowed  to  settle  for  a  few  hours. 
It  is  filtered  in  a  double  filter,  washed  with  water  containing  hydro- 
gen sulphide,  and  the  zinc  is  determined  as  sulphide  in  the  usual 
manner. 

The  filtrate  from  the  zinc  is  best  completely  evaporated  to  expel 
hydrogen  sulphide.  The  residue  is  taken  up  with  hydrochloric 
acid  and  water,  filtered  if  necessary,  and  the  cobalt  and  nickel  are 
then  precipitated  with  an  excess  of  caustic  potash.  They  are  first 
of  all  determined  together.  Should  a  separation  be  desired,  which 
as  a  rule  will  not  be  required  on  account  of  the  preponderance  of 
nickel,  one  of  the  usual  methods  is  employed. 

To  the  residual  liquid  and  precipitate  (^)  in  flask  (Z>~)  potassium 
or  sodium  hydrate  is  added  to  slight  alkaline  reaction.  A  sufficient 
quantity  of  light  yellow  potassium  or  sodium  sulphide  solution  is 
then  added,  together  with  TOO  c.c.  (=  one  -half)  of  the  liquid  in 
flask  (j9).  The  flask  is  then  placed  in  a  warm  place,  and  frequently 
agitated  to  bring  all  sulphides  of  antimony,  tin  and  arsenic  into 
solution.  It  is  then  diluted  to  3—4  liters  with  water  and  weighed, 
and  as  much  as  possible  of  the  clear  liquid  is  withdrawn.  The 
remainder,  together  with  flask  and  sediment,  is  weighed,  and  the 
amount  of  copper  corresponding  to  the  liquid  withdrawn  is  calcu- 
lated as  before.  The  flask  and  precipitate  are  preserved. 

In  order  to  estimate  antimony,  tin  and  arsenic,  the  liquid  is 
filtered,  if  necessary,  and  acidified  with  hydrochloric  acid.  The 
sulphides  of  these  metals  and  much  sulphur  are  precipitated.  These 
are  allowed  to  settle  for  a  time,  and  are  then  filtered  and  dried. 
Thereupon  precipitate  and  filter  are  placed  in  a  flask  and  extracted 
with  carbon  disulphide  to  free  from  the  greater  part  of  the  sulphur. 
The  solution  is  filtered  and  the  residue  is  warmed  with  dilute 
ammonium  sulphide,  whereby  the  sulphides  dissolve.  After  this 


64  CHEMICAL-TECHNICAL    ANALYSIS. 

has  been  filtered  and  the  filter  has  been  thoroughly  washed  it  is 
warmed,  and  pure  hydrogen  peroxide  is  added  until  the  color  has 
disappeared  and  the  sulphur  has  been  thoroughly  oxidized.  It  is 
now  evaporated  to  dryness  in  a  spacious  porcelain  dish  and  oxidized 
with  fuming  nitric  acid.  The  latter  is  expelled  as  far  as  possible, 
and  potassium  hydrate  is  added  to  distinct  alkaline  reaction,  after 
which  the  whole  is  washed  into  a  large  silver  crucible.  A  few  pieces 
of  stick  caustic  soda  are  placed  in  the  crucible,  which  is  heated 
carefully  in  a  sand-bath  until  the  water  has  been  completely  expelled. 
The  residue  is  then  gradually  heated  to  continued  fusion,  and  finally 
over  a  naked  flame.  The  crucible  contents,  now  perfectly  clear, 
are  lixiviated  with  water  until  the  insoluble  particles  have  separated 
as  a  powder,  when  about  ^  the  volume  of  alcohol  is  added.  The 
crucible  is  covered,  and  the  contents  are  occasionally  stirred  during 
the  24  hours  in  which  it  is  allowed  to  stand.  The  undissolved 
sodium  antimonate  is  filtered  and  washed  with  dilute  alcohol  (i :  i), 
to  which  a  few  drops  of  sodium  hydrate  solution  have  been  added. 
Stannate  and  arsenate  of  sodium  remain  in  the  filtrate  (-^).  The 
precipitate  of  sodium  antimonate  on  the  filter  is  repeatedly  covered 
with  a  warm  solution  of  tartaric  acid  in  dilute  hydrochloric  acid 
until  all  has  dissolved.  The  solution  is  diluted,  heated  and  precipi- 
tated with  hydrogen  sulphide.  Orange  sulphide  of  antimony  forms. 
Should  the  precipitate  be  rendered  dark  from  silver  sulphide  arising 
from  the  crucible,  it  is  redissolved  by  warming  with  ammonium 
sulphide,  filtered  from  the  sediment  and  reprecipitated  with  hydro- 
chloric acid.  The  hydrogen  sulphide  is  expelled  by  conducting 
into  the  flask  a  current  of  carbonic  acid.  It  is  then  filtered  on  a 
previously  dried  and  weighed  filter,  after  which  it  is  dried  and 
weighed.  To  expel  the  last  traces  of  water  and  sulphur  when  large 
quantities  of  antimony  sulphide  are  concerned,  an  aliquot  portion 
of  the  dried  precipitate  is  placed  in  a  porcelain  boat,  which  is 
introduced  into  a  glass  tube  and  moderately  heated.  Pure  dark -gray 
trisulphide  of  antimony  is  thus  obtained.  With  small  quantities  it 
suffices  to  wash  the  dried  precipitate  on  the  filter  repeatedly  with 
carbon  disulphide,  dry  and  weigh. 

Hydrochloric  acid  is  added  to  filtrate  (J?)  to  acid  reaction. 
Thereby  a  white  precipitate  of  arsenate  of  tin  now  and  then 
appears.  Without  taking  notice  of  this,  the  tin  and  arsenic  are 


CRUDE  AND  REFINED  COPPER.  65 

precipitated  with  a  current  of  hydrogen  sulphide.  These  are  fil- 
tered on  a  dried  and  weighed  filter,  washed  with  hydrogen  sulphide 
water,  dried  and  weighed.  A  separation  of  tin  from  arsenic  in  the 
precipitate,  which  usually  contains  a  considerable  amount  of  sulphur, 
is  conducted  in  the  following  way :  An  aliquot  portion  of  the  same 
is  placed  in  a  bulb  tube  bent  at  a  right  angle  on  one  side.  The 
straight  side  is  attached  to  a  hydrogen  sulphide  generator  by  means 
of  a  calcium  chloride  drying  tube.  The  bent  part  is  connected 
by  a  rubber  stopper  to  a  Peligot  tube  filled  with  ammonia  (about 
i  :  2).  This  tube,  finally,  may  be  attached  to  a  second  absorption 
vessel.  The  bulb  is  then  heated  in  a  current  of  hydrogen  sulphide. 
Sulphide  of  arsenic  and  sulphur  which  are  evolved  collect  in  the 
ammonia,  while  sulphide  of  tin  remains  in  the  bulb.  The  bulb- 
tube  is  detached  and  heated  strongly  in  a  current  of  air,  which  is 
conducted  through.  The  sulphide  of  tin  is  thereby  changed  to 
oxide,  and  this  is  weighed  on  cooling.  The  tin  is  calculated 
from  it. 

The  solution  of  sulphide  of  arsenic  is  washed  into  a  beaker, 
acidified  with  hydrochloric  acid,  chlorate  of  potash  is  added,  and 
the  liquid  is  warmed  moderately.  Sulphide  of  arsenic  dissolves. 
Any  sulphur  remaining  is  filtered  off.  The  arsenic  in  the  filtrate  is 
determined  as  magnesium  pyroarsenate  in  the  usual  manner,  and 
from  it  the  arsenic  is  calculated.  Bismuth  is  determined  by  re- 
peatedly adding  a  large  quantity  of  water  containing  sodium  sul- 
phide to  the  remaining  liquid  and  precipitate  in  flask  (-D),  shaking, 
and  drawing  off  as  much  liquid  as  possible.  The  residue  is  covered 
with  hydrochloric  acid,  nitric  acid  is  gradually  added,  and  the 
whole  is  allowed  to  stand  in  a  warm  place.  A  gradual  solution  of 
the  precipitate  takes  place,  with  separation  of  pure  sulphur.  Too 
energetic  action  causes  retention  of  copper  sulphide.  The  sulphur 
is  filtered  off,  washed,  and  the  solution  is  evaporated  repeatedly 
with  hydrochloric  acid.  When  the  latter  is  almost  completely  ex- 
pelled, water  is  added,  and  the  small  amount  of  residue  remaining 
is  filtered  off.  The  latter  consists  principally  of  basic  bismuth  chlo- 
ride. To  purify  the  same,  it  is  dissolved  in  dilute  hydrochloric 
acid,  treated  with  caustic  potash  to  alkaline  reaction,  potassium 
cyanide  is  added,  and  the  bismuth  is  precipitated  with  sodium  sul- 
phide, while  sulphide  Of  copper  remains  dissolved  in  the  cyanide 

5 


66  CHEMICAL-TECHNICAL    ANALYSIS. 

of  potash.  The  precipitate  is  thrown  on  a  previously  dried  and 
weighed  filter,  repeatedly  washed  with  carbon  disulphide,  and 
weighed  as  sulphide  of  bismuth. 

Sulphur  is  determined  by  adding  ammonia  to  400  c.c.  of  the 
liquid  remaining  in  (A),  until  the  greater  part  of  the  free  nitric  acid 
has  been  neutralized,  and  after  the  addition  of  a  few  drops  of 
barium  nitrate  solution  is  allowed  to  remain  in  a  warm  place.  In 
the  presence  of  appreciable  traces  of  sulphur,  probably  contained  in 
the  form  of  sulphurous  acid  in  the  copper,  a  small  precipitate  of 
barium  sulphate  is  formed  which  is  filtered  and  weighed. 

In  another  400  c.c.  solution  still  in  flask  (A),  the  phosphorus  is 
determined. 

To  accomplish  this  the  liquid  is  repeatedly  evaporated  with 
hydrochloric  acid  to  expel  nitric  acid.  The  residue  is  dissolved  in 
hot  water,  placed  in  a  weighed  flask  of  2  liters  capacity,  and  diluted 
with  hot  water  to  about  1200  c.c.  This  solution  is  completely,  pre- 
cipitated at  about  70°  C.  with  hydrogen  sulphide.  The  sulphides 
are  allowed  to  settle  and  as  much  clear  supernatant  liquid  as  possible 
is  drawn  off.  Flask,  remaining  liquid  and  precipitate  are  weighed, 
and,  as  before,  the  corresponding  amount  of  copper  in  the  sepa- 
rated liquid  is  calculated.  The  solution  is  filtered,  evaporated  to 
small  bulk  with  repeated  additions  of  nitric  acid,  and  the  phos- 
phorus is  determined  in  the  usual  manner.  (See  also  Chapter  V. , 
Fertilizers.)  The  method  of  Hampe  is  used  to  determine,  in  the 
bullion,  the  oxygen  which  is  combined  partly  with  metals  and  partly 
with  sulphur.  The  thoroughly  cleaned  copper  is  first  filed.  The 
filings  are  sieved  through  a  hair  sieve  and  the  iron  particles  are  with- 
drawn by  means  of  a  magnet.  The  powder  is  next  boiled  with 
dilute  caustic  potash  to  rid  it  of  traces  of  fat,  etc.  The  liquid  is 
poured  off,  and  the  powder  is  washed  and  hurriedly  dried. 

The  estimation  of  oxygen  is  calculated  by  loss  of  weight  upon 
ignition  in  a  current  of  hydrogen.  A  hard  glass  bulb  tube,  drawn 
out  at  both  ends,  is  suitable  for  this  purpose.  It  is  first  heated  in  a 
current  of  dry  air  and  then  allowed  to  cool.  It  is  weighed  ;  10-20 
grs.  dry  copper  powder  are  thereupon  placed  in  the  tube,  which  is 
reweighed.  Dry  carbonic  acid  from  a  Kipp  generator  is  then  con- 
ducted through  the  tube.  The  generator  is  set  in  action  two  hours 
before  use,  and  to  purify  and  dry  the  carbonic  acid  it  is  led  through 


CRUDE    AND    REFINED    COPPER.  67 

the  following  system  :  A  solution  of  bicarbonate  of  soda,  a  tube 
filled  with  lumps  of  bicarbonate,  a  wash-bottle  containing  silver 
nitrate  solution,  a  tube  containing  pumice-stone  saturated  with 
the  latter  solution,  a  wash-bottle  containing  cone,  sulphuric  acid, 
and  finally  a  calcium  chloride  tube.  The  carbonic  acid  is  allowed  to 
pass  through  the  tube  containing  the  copper  for  five  minutes,  after 
which  it  is  very  moderately  heated  to  free  from  all  traces  of  water. 
A  sublimate  of  arsenic  acid  will  form  when  the  heat  applied  is  too 
strong.  Pyrogenous  products  should  not  form.  Upon  cooling  in 
carbonic  acid,  the  latter  is  replaced  by  air  and  the  tube  is  weighed. 
The  loss  of  weight  should  equal  only  a  few  milligrams.  A  very 
slow  current  of  pure  hydrogen  is  then  conducted  over  the  copper. 
Thereupon  the  latter  is  at  first  moderately  heated,  and  later  to  glow- 
ing, for  about  fifteen  minutes.  During  the  application  of  heat, 
water  forms,  whereas,  with  impure  copper,  a  sublimate  of  arsenic, 
antimony  and  lead,  forms  in  the  bulb  and  adjacent  to  it.  This  sub- 
limate should  in  no  case  issue  from  the  tube.  Therefore  the  tube 
should  be  drawn  out  sufficiently  long,  and  the  hydrogen  current 
should  be  correspondingly  slow.  When  the  copper  contains  sul- 
phurous acid,  some  hydrogen  sulphide  is  evolved  with  the  steam. 
In  order  to  estimate  its  quantity,  the  gases  are  led  through  an  alka- 
line lead  solution  or  a  bromine-hydrochloric  acid  mixture,  and  the 
sulphur  is  estimated  from  the  sulphuric  acid  formed.  After  the 
copper  has  thoroughly  cooled  in  hydrogen,  dry  air  is  again  con- 
ducted through  and  the  tube  is  weighed.  The  loss  in  weight,  less 
the  sulphur  evolved  as  hydrogen  sulphide,  gives  the  amount  of 
oxygen  present. 


IV.  Alloys. 


1.  Phosphor-Bronze. 

THIS  usually  contains  copper,  tin  and  phosphorus,  and  frequently 
also  lead  and  zinc.  The  presence  of  other  constituents,  however, 
like  arsenic  and  iron,  is  not  excluded,*  on  account  of  which  a 
qualitative  analysis  should  always  be  conducted  first.  3  grams  of 
the  broken-up  alloy,  taken  for  quantitative  analysis,  are  covered 
with  water,  and  nitric  acid  is  carefully  added.  Heat  is  generated, 
and  decomposition  takes  place.  It  is  brought  to  a  finish  by  heating 
with  a  small  flame.  It  is  evaporated  to  dryness  in  a  porcelain  dish, 
dissolved  in  nitric  acid,  and  water  is  added,  after  which  it  is  filtered 
and  washed  out  with  hot  water  (—  residue  A  and  filtrate  B). 

Residue  A  contains  all  the  tin,  together  with  all  phosphorus  (as 
phosphate  of  tin),  some  copper  and  some  of  the  lead.  It  is  ignited 
and  weighed.  Thereupon  it  is  fused  in  a  porcelain  crucible  with 
carbonate  of  soda  and  sulphur.  The  fusion  is  lixiviated  with  hot 
water.  The  small  residue  is  filtered  off,  and  estimated  either  directly 
as  subsulphide  of  copper  by  ignition  with  sulphur  in  an  atmosphere 
of  hydrogen,  or  else,  if  necessary,  a  separation  of  copper  from  lead 
is  carried  out  by  means  of  sulphuric  acid  in  nitric  acid  solution. 
The  filtrate  containing  the  phosphoric  acid  and  tin  is  acidified 
with  hydrochloric  acid.  The  sulphide  of  tin  is  filtered  off,  the 
filtrate  evaporated  to  dryness  on  a  water-bath,  and  taken  up  with 
nitric  acid.  The  phosphoric  acid  is  precipitated  with  molybdate 
solution,  and  the  determination  is  continued  in  the  usual  manner. 
The  copper,  calculated  into  cupric  oxide,  plus  the  phosphoric 
anhydride  formed  from  the  phosphorus,  is  deducted  from  the  total 
residue,  and  the  remainder  is  calculated  as  oxide  of  tin. 

The  filtrate  B,  after  addition  of  sulphuric  acid,  is  evaporated  to 
dryness,  to  precipitate  lead,  and  the  sulphuric  acid  completely 

#  No  account  of  the  presence  of  these  is  taken  in  the  following  method  of  quan- 
titative analysis. 


WHITE    METAL.  69 

expelled.  The  residue  is  then  taken  up  with  water,  washed  with 
water  containing  sulphuric  acid,  then  with  alcohol,  and  is  finally 
ignited  and  weighed.  Filtrate  from  the  lead  sulphate  is  placed  in  a 
250  c.c.  graduated  flask,  and  diluted  to  the  mark.  In  one  portion  of 
50  c.c.  the  copper  is  estimated  as  sulphide  by  means  of  hydrogen 
sulphide,  while  in  the  remaining  200  c.c.  the  metals  present  in  less 
quantity  may  be  determined.  For  this  purpose  copper  is  precipi- 
tated with  hydrogen  sulphide,  and  filtered  off.  The  nitrate  is 
evaporated  to  dryness,  taken  up  with  a  few  drops  of  hydrochloric 
acid,  neutralized  exactly  with  sodium  carbonate,  and  hydrogen 
sulphide  is  run  in.  Sulphide  of  zinc  is  precipitated.  Upon  addi- 
tion of  a  few  drops  of  a  dilute  solution  of  sodium  acetate  and 
renewed  addition  of  hydrogen  sulphide,  the  precipitation  is  com- 
pleted. The  precipitate  is  allowed  to  stand  for  a  time,  filtered,  and 
determined  as  zinc  sulphide  by  ignition  with  sulphur  in  a  current  of 
hydrogen.  To  the  copper  contained  in  the  filtrate  B,  that  which  was 
contained  in  residue  A  must  be  added.  The  same  holds  good  for 
any  lead  found  in  the  residue. 

2.  White  Metal. 

This  contains  tin,  as  a  rule,  as  chief  constituent,  together  with 
antimony  and  also  zinc.  Copper  and  lead  are  frequently  present  in 
minute  quantities,  although  sometimes  in  large  quantities.  Arsenic, 
mercury,  nickel  and  iron  may  be  present.  The  quantitative  analysis 
covering  the  presence  of  tin,  antimony,  copper,  lead  and  zinc  will 
be  described. 

1-2  grs.  alloy  are  dissolved  in  nitric  acid,  as  previously  described, 
evaporated  nearly  to  drynesss,  taken  up  with  dilute  nitric  acid, 
filtered,  and  washed  with  water  containing  ammonium  nitrate. 
(Filtrate  A.  Residue  B. ) 

Filtrate  A  contains  copper,  lead  and  zinc,  whose  separation  is 
conducted  as  given  under  Phosphor-Bronze. 

Residue  B  contains  all  tin  and  antimony,  besides  small  quantities 
of  copper,  lead  and  zinc.  It  is  dried,  ignited  and  weighed.  A 
weighed  portion  of  the  same  is  fused  with  soda  and  sulphur,  and 
the  fusion  is  lixiviated  with  water.  Should  the  residue  be  small,  it 
may  be  directly  ignited  with  sulphur  in  a  current  of  hydrogen,  and 
considered  as  the  sulphide  of  one  of  the  three  metals,  copper,  lead 


70  CHEMICAL-TECHNICAL   ANALYSIS. 

and  zinc,  depending  on  the  predominance  of  one  or  another  as 
shown  by  the  qualitative  tests  or  the  quantitative  analysis  of  filtrate 
A.  Should  there  be  considerable  residue,  it  is  dissolved  in  hot 
dilute  nitric  acid,  and  the  individual  constituents  are  separated  and 
determined.  The  amount  of  these  (in  form  of  oxides)  is  deducted 
from  the  substance  used  for  fusion,  whereby  tin  oxide  and  antimony 
oxide  (SnO2  and  Sb2O4)  remain.  These  are  recalculated  from  the 
aliquot  portion  used  on  the  total  residue.  In  order  to  separate  tin 
and  antimony,  another  portion  of  the  residue  B  is  fused  with  caustic 
soda  in  a  silver  crucible,  and  the  fusion  is  lixiviated  until  the  insol- 
uble portion  is  powdered.  One-half  volume  of  alcohol  is  added, 
and  allowed  to  stand  24  hours  with  repeated  stirring.  It  is  then 
filtered  off  and  washed  with  dilute  alcohol  (i  :  2).  The  sodium 
antimonate  remaining  in  the  filter  contains  a  small  quantity  of  cop- 
per, whereas  traces  of  lead  or  zinc  will  remain  in  solution  with  the 
tin,  and  can  be  precipitated  by  careful  addition  of  sodium  sulphide. 
After  filtration  from  this  minute  precipitate,  hydrochloric  acid  is 
added  to  precipitate  tin  sulphide,  which  is  quantitatively  estimated 
as  tin  oxide  by  careful  oxidation  and  ignition  with  ammonium  car- 
bonate. If  this  be  calculated  on  the  total  residue,  and  subtracted 
from  the  sum  of  the  oxides  of  tin  and  antimony  previously  found, 
there  remains  the  antimony  tetroxide,  from  which  antimony  is 
calculated. 

3.  Iron  Alloys. 

Iron  is  alloyed  with  other  substances  besides  those  mentioned 
under  the  investigation  of  iron,  in  order  to  impart  to  it  certain 
properties,  principally  hardness  and  toughness.  Some  of  these 
substances  are  chromium,  tungsten,  titanium,  aluminium  and 
nickel.  For  instance,  there  is  contained  in  tungsten  steel  9  per 
cent.  W.  ;  in  chromium  steel,  2-4  per  cent.  Cr.  ;  in  ferro-chrom, 
29-49  per  cent.  Cr.  ;  in  ferro-aluminium,  6.8-10  per  cent.  Al., 
and  in  nickel  steel,  8-10  per  cent.  Ni.  With  reference  to  chro- 
mium and  nickel  estimations,  ferro-chrom  and  nickel  steel  serve  as 
illustrations  of  such  alloys. 

Ferro-chrom. — 1-4  grs.  of  sample,  powdered  as  fine  as  possible, 
are  boiled  ^  hour  in  a  large  beaker  with  500  c.c.  water  and  50  c.c. 
sulphuric  acid  (i  :  i).  Usually  all  dissolves.  Should  a  residue 
remain,  however,  after  continued  heating,  it  is  filtered  off,  washed, 


IRON    ALLOYS.  71 

incinerated  in  a  platinum  capsule,  and  fused  with  a  mixture  of  two 
parts  fused  borax  and  three  parts  soda  for  three  hours  at  a  high 
heat,  preferably  in  a  muffle.  The  fusion  is  dissolved  in  water, 
acidified  with  sulphuric  acid,  and  added  to  the  first  filtrate.  The 
united  filtrates  are  brought  to  boiling,  and  a  concentrated  perman- 
ganate solution  is  added  to  the  same  until  red  coloration  sets  in. 
The  excess  of  permanganate  is  reduced  with  manganous  sulphate, 
after  which  it  is  washed  into  a  liter  flask  filled  to  the  mark  after 
cooling,  well  shaken,  and  filtered  through  a  ribbed  filter.  An  ali- 
quot part  of  this  solution,  which  is  colored  yellow  in  presence  of 
the  smallest  quantities  of  chromium,  is  treated  with  50  or  100  c.c. 
ferrous  ammonium  sulphate  solution  (containing  20  grams  of  the 
salt  and  10  c.c.  sulphuric  acid  (i  :  i)  to  the  liter),  after  which  the 
excess  of  ferrous  salt  is  titrated  back  with  -&  normal  permanganate. 
At  the  same  time  the  same  quantity  of  ferrous  ammonium  sulphate 
solution  is  titrated  with  permanganate,  and  from  the  quan- 
tity of  the  latter  now  used  the  first  is  deducted.  The  differ- 
ence represents  the  ferrous  oxide  oxidized  by  the  chromic  acid  from 
which  chromium  can  easily  be  calculated.  2CrO3  =  6  Fe  O. 

Nickel  steel. — 2-4  grs.  sample  are  dissolved  in  nitric  acid  (sp.  gr. 
1.2).  After  dissolving,  10—20  c.  c.  sulphuric  acid  (i  :  i)  are  added, 
and  the  whole  is  evaporated  until  sulphuric  acid  begins  to  volatilize. 
The  residue  is  dissolved  in  water,  and  the  solution  is  gradually 
poured  into  a  500  c.c.  flask  in  which  50  c.c.  sulphate  of  ammonium 
solution  (containing  500  grs.  of  the  salt  in  a  liter  of  water)  and  130 
c.c.  cone,  ammonia  have  previously  been  placed.  It  is  then  diluted 
to  the  mark,  well  mixed,  and  filtered  through  a  ribbed  filter.  Two 
hundred  and  fifty  c.c.  of  the  filtrate  are  taken,  and  in  this  the 
nickel  is  determined  either  electrolytically  or  by  precipitation 
with  ammonium  sulphide,  or  hydrogen  sulphide,*  in  a  solution 
slightly  acidified  with  acetic  acid.  In  case  copper  was  present  in 
the  nickel  steel,  it  will  be  found  in  the  ammoniacal  solution.  The 
copper,  in  the  solution  strongly  acidified  with  hydrochloric  acid, 
may  be  removed  with  hydrogen  sulphide.  Estimation  of  nickel  is 
then  conducted  with  the  filtrate. 

*  In  the  latter  case  the  precipitate  of  nickel  sulphide  is  dissolved  in  hydro- 
chloric acid,  with  addition  of  nitric  acid  or  potassium  chlorate,  and  then  precipi- 
tated with  caustic  potash.  It  is  finally  transformed  into  metallic  nickel  by  reduc- 
tion in  a  current  of  hydrogen. 


V.  Fertilizers. 


THESE  may  be  divided  into  three  groups,  according  to  their  active 
constituents:  i.  Phosphate  fertilizers;  2.  Potash  fertilizers;  3. 
Nitrogenous  fertilizers.  In  addition  to  these,  mixed  fertilizers  are 
used  which  may  contain  all  three  constituents. 

Combined  methods  exist  for  the  estimation  of  phosphoric  acid, 
potash  and  nitrogen.  These  will  be  described  first  of  all. 

(a)  Phosphoric  Acid. 

Phosphoric  acid  may  be  determined  gravimetrically  or  volumet- 
rically.  The  gravimetric  methods  are  the  molybdate  and  citrate 
methods.  In  both  the  phosphoric  acid  is  determined  finally  as 
magnesium  pyrophosphate.  It  is  determined  volumetrically  by 
titration  with  uranium  acetate. 

(a)  Molybdate  method.  Separation  from  all  other  bases  is 
accomplished  by  use  of  ammonium  molybdate,  whereby  all  phos- 
phoric acid  is  precipitated  in  the  form  of  a  compound  of  varying 
composition.  Phosphoric  acid  is  determined  from  this. 

To  do  this,  200  c.c.  molybdate  solution  are  added  to  a  solution 
containing  phosphoric  acid  (not  exceeding  .2  gr.  P2O5),  which  is 
then  kept  for  15-20  minutes  at  a  temperature  of  70—80°  C.  After 
standing  three  hours  the  supernatant  liquid  is  filtered  off,  and  the 
precipitate,  as  much  as  possible  of  which  is  allowed  to  remain  in 
the  beaker,  is  washed  with  a  1 5  per  cent,  solution  of  ammonium 
nitrate,  containing  10  c.c.  nitric  acid  to  the  liter.  The  washings 
are  thrown  on  the  same  filter.  The  beaker,  holding  the  main  por- 
tion of  precipitate,  is  placed  under  the  funnel.  A  warm  2^  per 
cent,  ammonia  solution  is  poured  on  the  filter  in  just  sufficient 
amount  to  dissolve  the  precipitate  upon  it.  It  is  then  washed  with 
cold  ammonia  of  the  same  strength  until  a  red  coloration  (molyb- 
date reaction)  no  longer  appears  on  adding  ferrocyanide  of  potassium 
to  a  drop  of  the  filtrate  placed  on  a  porcelain  plate.  The  quantity 


FERTILIZERS.  73 

of  ammonia  used  (150  c.c.)  should  just  about  suffice  to  dissolve 
the  precipitate  in  the  beaker  on  shaking.  If  not,  more  ammonia 
is  added,  and  a  clear  solution  is  obtained.  To  this,  for  every  .  i  gr. 
P2O5,  TO  c.  c.  magnesium  mixture  are  added,  drop  by  drop.  It  is 
stirred  for  some  time  without  touching  the  sides  of  the  beaker,  and 
is  filtered  after  at  least  three  hours'  standing.  The  precipitate  is 
washed  with  2  ^  per  cent,  ammonia  until  a  portion  of  the  filtrate, 
acidified  with  nitric  acid,  opalesces  but  slightly.  Further  manipu- 
lation is  conducted  in  the  usual  manner. 

Reagents  used  are  prepared  as  follows  : 

Molybdate  solution  :  150  grams  crystallized  ammonium  molybdate 
and  400  grams  ammonium  nitrate  are  dissolved  in  a  liter  of  water, 
and  the  solution  is  poured  into  an  equal  volume  of  nitric  acid  (sp. 
gr.  1.19).  The  solution  should  be  kept  in  the  dark. 

Magnesium  mixture:  100  grams  magnesium  chloride  and  140 
grams  ammonium  chloride  are  dissolved  in  1300  c.c.  water,  and 
diluted  to  two  liters  with  24  per  cent,  ammonia.  It  is  filtered  after 
standing  in  a  stoppered  flask  for  several  days. 

(j3)  Citrate  method.  By  use  of  this  method  the  precipitation  of 
phosphates  of  lime,  iron,  etc. ,  by  ammonia  is  prevented  by  citric  acid. 

A  quantity  of  solution  containing  phosphoric  acid  (not  exceeding 
.2  gr.  P2O.)  is  treated  with  100  c.c.  citrate  solution  (prepared  by 
dissolving  150  grs.  citric  acid  in  water,  adding  500  c.c.  24  per  cent, 
ammonia,  and  diluting  to  1500  c.c.).  If  necessary,  more  ammonia 
is  added,  whereby  turbidity  must  not  ensue.  The  excess  is  neutral- 
ized with  a  few  drops  of  nitric  acid,  and  25  c.c.  magnesium  mixture 
are  added.  The  precipitate  is  treated  as  under  (a). 

The  method  is  easily  carried  out  and  is  much  used.  Since  on 
the  one  hand  some  magnesium  ammonium  phosphate  is  dissolved 
by  the  excess  of  citric  acid,  and,  on  the  other  hand,  small  quantities 
of  phosphate  of  lime,  etc.,  are  precipitated,  the  errors  are  balanced. 

(r)  Uranium  method.  This  method,  which  is  considered  as 
universally  known,  can  only  be  used  to  determine  water-soluble 
phosphoric  acid.  It  is  now  rarely  used,  at  any  rate. 

(b)  Potassium  Oxide. 

This  is  determined  as  the  double  salt  2KCl.PtCl4  by  using  pla- 
tinic  chloride.  It  is  only  necessary  that  nothing  but  chlorides  be 


74  CHEMICAL-TECHNICAL    ANALYSIS. 

present,  of  which  those  of  sodium,  calcium  and  magnesium  form 
platinum  salts,  soluble  in  alcohol,  whereas  that  of  potassium  chlo- 
ride is  insoluble. 

Should  there  be  sulphates  present,  as  is  usually  the  case,  they  are 
converted  into  chlorides  by  adding  a  boiling  chloride  of  barium 
solution  (avoiding  excess  as  much  as  possible)  to  the  liquid,  to 
which  i  c.c.  hydrochloric  acid  has  been  added,  without  regarding 
a  possible  residue.  The  filtrate,'  or  an  aliquot  portion  of  the  same, 
is  evaporated  down  to  about  15  c.c.  bulk,  and  sufficient  platinic 
chloride  is  added  to  convert  all  salts  present  into  double  salts  ( i 
gr.  platinum  to  .5  gr.  substance).  It  is  stirred  with  a  glass  rod, 
evaporated  to  about  10  c.c.,  and  90  per  cent,  alcohol  is  added. 
After  stirring  for  a  while,  and  permitting  to  stand,  it  is  filtered  on 
a  filter,  moistened  with  alcohol,  and  washed  with  alcohol  until  the 
washings  have  become  colorless. 

The  precipitate  may  be  dried  at  130°  and  weighed.  But  since 
it  can  contain  small  quantities  of  chlorides  insoluble  in  alcohol,  it  is 
better  to  incinerate,  filter  and  place  contents  in  a  porcelain  crucible, 
and  to  ignite  the  residue  separately  with  small  quantities  of  pure 
oxalic  acid  at  a  high  temperature. 

(c)  Nitrogen. 

Nitrogen  can  be  present  as  ammonia  (ammonium  salts),  as  nitrates, 
or  as  organic  nitrogenous  compounds.  It  may  finally  be  present  as 
a  combination  of  two  or  three  of  these  forms. 

(a)  Nitrogen  as  ammonia.  The  estimation  is  carried  out  by 
heating  with  caustic  soda  and  absorbing  the  ammonia  evolved  in 
standardized  acid.  The  operation  is  well  known.  When  nitrogenous 
organic  matter  is  simultaneously  present,  which  is  partially  decom- 
posed by  boiling  caustic  soda  with  formation  of  ammonia,  soda- 
lime  or  freshly  calcined  magnesia  is  used. 

(/?)  Nitrogen  as  nitrates  is  estimated  in  an  eudiometer  graduated 
into  tenths,  as  nitric  oxide,  which  is  caught  up  after  liberation  from 
the  nitric  acid,  which  is  reduced  with  ferrous  chloride  (method  of 
Schulze-Tiemann  or  Schlosing- Wagner). 

(>)  Organic  nitrogen.  Various  methods  proposed  for  this  esti- 
mation have  been  replaced  by  the  method  of  Kjeldahl,  the  modi- 
fied form  of  which,  by  Wilfarth,  will  be  described  here.  1-2  grs. 
substance  are  covered  with  20  c.c.  cone,  sulphuric  acid  in  a  long- 


FERTILIZERS.  75 

necked,  round-bottom  flask  of  about  150  c.c.  capacity.  .7  gr.  freshly 
prepared  yellow  mercuric  oxide  (or  .5  gr.  mercury)  is  added,  and  the 
whole  is  heated  on  a  wire  gauze,  at  first  moderately,  and  finally  to 
a  brisk  boiling.  It  is  better  to  fasten  the  flask  in  a  clamp  in  an  in- 
clined position  in  order  to  avoid  loss  by  sputtering,  and  also  to  avoid 
the  direct  heating  of  the  frequently  uneven  bottom  of  the  flask. 

The  liquid  is  heated  until  colorless.  It  is  allowed  to  cool  and  is 
poured  into  an  Erlenmeyer  flask  of  about  3^  liter  capacity,  con- 
taining some  water,  and  is  then  thoroughly  rinsed  out.  After  cool- 
ing, an  excess*  of  about  30  per  cent,  caustic  soda  is  added,  together 
with  25  c.c.  of  a  10  per  cent,  potassium  sulphide  solution.  The 
latter  precipitates  all  the  mercury  in  the  form  of  mercuric  sulphide 
and  simultaneously  decomposes  the  mercury  amides,  from  which  the 
ammonia  is  expelled  very  slowly  by  alkalies.  A  few  pieces  of  gran- 
ulated zinc  are  added,  to  prevent  bumping  on  distillation. 

By  distilling,  all  the  ammonia  is  volatilized  and  is  collected  in  a 
receiver  containing  20  c.c.  of  half-normal  sulphuric  acid  and  50 
c.c.  of  water.  The  excess  of  acid  is  titrated  and  the  nitrogen  is 
calculated  (iH.2SO4is  equivalent  to  2N).  In  order  to  prevent 
alkali  from  being  carried  over,  different  forms  of  apparatus  have 
been  proposed.  As  a  rule,  a  bulb  tube  is  placed  in  the  flask 
and  connected  with  a  condenser.  Distillation  is  finished  at  the  end 
of  from  20-30  minutes.  The  contents  of  the  flask  usually  heat  up 
considerably,  but  a  loss  of  ammonia  is  not  to  be  feared,  even  when 
not  cooled. 

The  most  important  fertilizers  belonging  to  each  of  the  three 
groups  will  now  be  described. 

1.  Phosphate  Fertilizers. 

They  may  be  divided  into  : 


A.   Phosphates  containing  water-insoluble 
phosphoric  acid. 

(a).  Crude  phosphates.  |  (£).      Artificially-pre- 


Mineral  phosphates. 
Bone  phosphates. 
Guano  phosphates. 


pared  phosphates. 
Phosphate  slags. 


B.   Phosphates          containing 
•water-sohible  phosphoric  acid. 

Superphosphates . 


*  The  amount  necessary  is  easily  calculated  approximately  from  the  sulphuric 
acid  used. 


76  CHEMICAL-TECHNICAL    ANALYSIS. 

A.  Phosphates  Containing  "Water-Insoluble  Phosphoric  Acid. 

Contain  phosphoric  acid  principally  in  form  of  tricalcium  phos- 
phate, which,  together  with  iron  and  aluminium  present,  is  very 
slowly  soluble. 

In  order  to  determine  phosphoric  acid  in  crude  phosphates  of 
sub-group  (0) — phosphorite,  apatite,  bone  meal,  animal  charcoal  and 
Baker  guano,  5  grs.  substance,  finely  powdered,  are  boiled  with  20 
c.c.  cone,  nitric  acid  and  50  c.c.  cone,  sulphuric  acid  for  ^  hour, 
and  the  solution,  plus  residue,  is  poured  into  a  ^  -liter  graduated 
flask,  diluted  to  the  mark  and  thoroughly  agitated,  after  which  it  is 
filtered  through  a  dry  ribbed  filter.  In  50  c.c.  of  the  filtrate  the 
phosphoric  acid  is  determined  by  the  molybdate  method. 

Should  the  citrate  method  be  preferred,  however,  the  substance 
is  dissolved  in  30  c.c.  concentrated  sulphuric  acid,  instead  of  the 
above  mixture.  The  remaining  operation  is  conducted  as  in  p 

(P.  73)- 

A  nitrogen  determination,  according  to  Kjeldahl,  as  well  as  the 
detection  of  less  valuable  phosphates,  is  usually  undertaken  in  bone- 
dust.  The  latter  is  detected  by  a  high  percentage  of  matter  insolu- 
ble in  hydrochloric  acid  (sand)  and  presence  of  ferric  oxide  and 
alumina. 

Thomas  slag  is  the  most  important  product  of  the  phosphate  slags 
in  sub-group  (<£).  To  determine  the  phosphoric  acid  in  this,  10  grs. 
powdered  material  are  moistened  with  water,  and  stirred  with  5  c.c. 
of  a  mixture  of  equal  parts  sulphuric  acid  and  water.  As  soon  as 
the  mass  begins  to  harden,  50  c.c.  concentrated  sulphuric  acid  are 
added,  and  the  whole  is  heated  for  ^  -hour  on  a  sand-bath  until 
white  vapors  arise.  Meanwhile  the  mass  is  continually  stirred. 
After  cooling,  it  is  carefully  diluted  with  water,  washed  into  a 
YZ  -liter  flask,  diluted  to  the  mark,  well  mixed,  and  allowed  to  stand 
several  hours,  in  order  to  allow  gypsum  to  separate.  It  is  then 
filtered  through  a  dry  ribbed  filter,  and  the  phosphoric  acid  is  deter- 
mined in  50  c.c.  filtrate  by  the  citrate  method. 

B.  Phosphates  Containing  Water-Soluble  Phosphoric  Acid. 
To  these  belong  principally  the  superphosphates  obtained  by  dis- 
solving crude  phosphates  in  sulphuric  acid,  and  which  contain  the 
monocalcium  phosphate  CaH4(PO4)2,  which    is   soluble   in  water. 


FERTILIZERS.  77 

Since  the  decomposition,  however,  is  never  perfect,  there  are 
present,  beside  these,  di-  and  tri calcium  phosphate,  the  quantity  of 
which  increases  on  standing  for  a  long  time,  due  to  the  action  of 
aluminium  and  iron  compounds  present.  The  latter  process  is 
termed  phosphoric  acid  reversion. 

The  phosphoric  acid  in  commercial  phosphates  is,  therefore, 
present  in  three  forms  : 

(a)  Monocalcium  phosphate,  CaH4(PO4\.  This  is  soluble  in 
water,  and,  together  with  free  phosphoric  acid,  is  estimated  as 
water-soluble  phosphoric  acid. 

(3)  Dicalcium  phosphate,  CaHPO4.  This  is  insoluble  in  water, 
but  is,  on  the  contrary,  soluble  in  ammonium  citrate.  At  times  it 
is  determined,  together  with  the  phosphoric  acid  present  in  form  of 
iron  or  aluminium  phosphate,  as  ''citrate-soluble"  or  "reverted" 
phosphoric  acid. 

(c)  Tricalcium  phosphate,  Cas(PO4)a,  is  insoluble  in  water  and 
ammonium  citrate.  The  phosphoric  acid  corresponding  to  this  is 
designated  as  insoluble  phosphoric  acid. 

(«)  Estimation  of  water-soluble  phosphoric  acid. 

Twenty  grams  of  superphosphate  are  placed  in  a  liter  flask,*  and 
thoroughly  agitated  for  yz  hour  with  800  c.c.  water.  The  liquid  is 
then  diluted  to  the  mark,  well  mixed,  filtered  through  a  dry  ribbed 
filter,  and  the  phosphate  is  determined  by  the  citrate  method  in 
50  c.c.  filtrate. 

(/?)  Estimation  of  total  phosphoric  acid. 

Five  grams  of  superphosphate  are  suspended  in  20  c.c.  water,  and 
then  boiled  with  100  c.c.  concentrated  nitric  acid  for  ^  hour. 
The  mixture  is  washed  into  a  ^ -liter  flask,  diluted  to  the  mark, 
filtered  through  a  dry  ribbed  filter,  and  the  phosphoric  acid  is  de- 
termined in  50  c.c.  filtrate  by  the  molybdate  method.  The  estima- 
tion of  citrate-soluble  phosphoric  acid,  concerning  the  value  of 
which  views  differ,  will  not  be  further  described. 

2.  Potassium  Fertilizers. 

The  main  source  of  these  is  the  discarded  Stassfurter  salts,  which 
consist  chiefly  of  potassium  and  magnesium  salts.  The  most  im- 
portant are  Sylvite,  5KC1  +  NaCl ;  Carnallite,  KC1  +  MgCl2  -f 

*  Agitators  worked  by  hand  or  water-power  are  very  convenient. 


78  CHEMICAL-TECHNICAL    ANALYSIS. 

6H,O  ;  Kainite,  KC1  -f  MgSO4  -f  3H2O  ;  and  Schonite,  K2SO4  + 
MgSO4  +  6H2O. 

In  these  the  per  cent,  of  potassium  oxide  is  usually  determined 
by  one  of  the  methods  mentioned  (p.  73). 

3.  Nitrogenous  Fertilizers. 

According  to  the  division  previously  given,  there  belong  in  this 
group  ammonium  sulphate,  potassium  and  sodium  nitrates  or  a  mixture 
of  both  (with  an  average  percentage  of  nitrogen  equalling  14.5-16 
per  cent.),  dried-blood  powder  (12-15  per  cent.  N,  about  i  per 
cent.  P2O5),  horn  meal  (7-14  per  cent.  N,  5-6  per  cent.  P2O5),  pow- 
dered hide  (6-10  percent.  N). 

4.  Mixed  Fertilizers. 

These  are  artificial  mixtures  of  phosphorus,  potassium  and  nitro- 
genous fertilizers,  such  as  potassium -superphosphate,  ammonium- 
superphosphate,  saltpeter -superphosphate  or  natural  products.  To 
the  latter  belong  Peru  guano,  dried-meat  powder,  fish-guano  and 
dung. 

Peru  guano,  formed  from  bird  excrement  and  carcasses  of  marine 
animals,  but  less  weathered  than  guano  phosphate,  contains,  on  the 
average,  8-n  per  cent,  nitrogen  and  10-20  per  cent,  phosphoric 
acid. 

Dried  meat  powder,  made  out  of  meat  and  bones  of  dead  ani- 
mals, contains  6-7  per  cent,  nitrogen  and  10-15  per  cent,  phos- 
phoric acid.  Fish  guano,  made  out  of  fish  refuse,  contains  5-12 
per  cent.  N,  13-16  per  cent.  P2O5. 

Dung,  the  mixture  of  solid  and  fluid  excrement  of  cattle,  horses, 
sheep,  swine,  together  with  litter,  contains  all  three  plant-nour- 
ishers  in  varying  amounts.  They  may  be  confined  within  the  fol- 
lowing limits:  Potassia,  .40-. 6 7  per  cent.;  phosphoric  acid, 
.16-. 28  per  cent.,  and  nitrogen,  .34-. 83  percent. 


VI.  Sugar  Industry. 


THE  investigation  of  sugar  and  saccharine  products,  such  as  beets, 
thin  juice,  molasses,  etc.,  extends  as  a  rule  to  the  estimation  of 
cane  sugar,  invert  sugar,  water,  alkalinity,  ash,  and  sometimes 
color. 

Concerning  the  methods  employed  for  this  purpose  the  follow- 
ing may  be  said : 

(a)  Cane  sugar.  This  may  be  determined  from  the  specific 
gravity  or  by  polarization. 

(a)  Specific  gravity.  Only  in  pure  sugar  solutions  can  sugar  be 
estimated  by  means  of  specific  gravity.  Should  other  substances 
be  in  solution,  they  effect  the  specific  gravity  in  different  ways. 
In  such  solutions  only  an  apparent  value  (for  dry  substance)  ex- 
pressed in  per  cent,  of  sugar,  can  be  obtained. 

The  determination  of  specific  gravity  is  conducted  either  with 
one  of  the  usual  forms  of  applicable  apparatus,  such  as  densimeter, 
pyknometer,  hydrostatic  balance,  in  which  cases  the  percentage  of 
sugar  corresponding  to  the  specific  gravity  must  be  referred  to  in  a 
corresponding  table,  or  by  means  of  an  areometer  specially  con- 
structed for  the  purpose,  the  saccharometer  of  Balling  or  Brix.  On 
account  of  its  graduation  direct  sugar  percentage  readings  can  be 
made.  In  this  case  it  is  advantageous  to  use  such  saccharometers 
on  which  the  scale  is  extended  over  a  set  of  several  consecutive 
spindles,  and  on  which  tenths  per  cent,  can  be  easily  read. 

When  the  saccharometers  are  used  to  read  volume  percentage, 
an  error,  provided  for  on  the  instrument,  due  to  change  in  volume 
by  temperature,  is  taken  into  account. 

Pyknometers  and  hydrostatic  balance  are  then  used  when  only 
small  quantities  of  substance  are  obtainable. 

(/?)  Polarization.  It  is  taken  for  granted  that  the  principle  on 
which  these  instruments  rest,  as  well  as  the  arrangement  of  the 
same,  is  known.  Recently  the  apparatus  of  Soleil-Ventzke-Scheib- 


80  CHEMICAL-TECHNICAL    ANALYSIS. 

ler  and  the  half-shadow  apparatus  of  Schmidt  and  Haensch,  have 
come  into  use.  The  former  is  adjusted  for  a  transition  color,  a 
pale  bluish  violet,  the  latter  for  an  even,  faint  shadow  on  both 
halves.  The  normal  weight  for  both  forms  equals  26.048  grams; 
that  is,  a  solution  of  26.048  grs.  pure  cane  sugar  in  100  c.c.  in 
a  tube  200  mm.  in  length  causes  a  rotation  of  100°,  or  i°  corres- 
ponds with  .26048  gr.  sugar  in  100  c.c.  With  the  use  of  this 
normal  weight  and  normal  tube  (200  mm.)  the  per  cent,  of  sugar 
can  consequently  be  read  off  directly.  When  a  100  mm.  or 
400  mm.  tube  is  used,  the  degrees  are  to  be  doubled  or  halved. 

Polarization  is  always  preceded  by  clarification  and  decoloriza- 
tion  with  a  solution  of  lead  acetate  (basic  lead  acetate).  Cane 
sugar  is  dextro -rotary  (  +  );  invert  sugar  laevo-rotary  ( — ). 

(£)  Invert  sugar  possesses  the  property  of  reducing  Fehling's 
solution  (see  Reagents,  p.  90)  with  separation  of  suboxide  of 
copper.  On  the  basis  of  this  precipitated  suboxide,  which  is  reduced 
to  metallic  copper,  the  amount  is  determined  by  a  method  described 
later.  The  results  obtained  by  polarization  are  influenced  by  the 
laevo-rotary  power  of  invert  sugar.  Therefore,  in  the  presence  of 
the  latter  a  different  procedure,  that  of  Clerget,*  is  followed  in  the 
estimation  of  cane  sugar.  The  description  of  this  is  given  further 
on. 

Syrup,  molasses,  etc. ,  frequently  contain  invert  sugar. 

(*:)  Water.  The  use  of  small,  flat-bottomed  porcelain  or  enam- 
eled sheet-iron  capsules  is  advisible  for  fluid  or  semi-fluid  products. 
Drying  is  done  on  a  water-bath  or  in  an  air  bath  at  80-90°  to  be- 
gin with.  Further  drying  should  take  place  at  105°  under  the  in- 
fluence of  a  current  of  dry  air,  in  order  to  expel  the  last  traces  of 
water.  Stammer  recommends  the  use  of  a  special  apparatus  for 
this  purpose.  In  the  absence  of  the  latter  an  ordinary  air-bath  is 
made  to  answer. 

It  is  also  recommended  to  mix  the  substance  with  a  glass  rod 
(4-5  grs.  molasses,  8-10  grs.  syrup  and  dense  juices)  with  20  grs. 
ignited  quartz  sand,  free  from  dust,  in  a  small  porcelain  capsule. 
This  is  then  weighed  and  placed  in  an  air-bath  at  100°  for  %  hour. 
It  is  then  thoroughly  stirred  with  a  rod  until  a  homogeneous 
mass  is  obtained  and  dried  in  an  air-bath  to  constant  weight. 

*  The  same  method  is  also  made  use  of  in  the  presence  of  raffinose. 


SUGAR    INDUSTRY.  81 

(V)  Alkalinity.  This  is  influenced  by  the  presence  of  free 
alkali,  lime  and  free  ammonia  in  the  saccharine  substance. 

It  is  estimated  by  titration  with  normal  or  one-tenth  normal  acid, 
usually  nitric  acid,  and  is  calculated  into  per  cent.  lime. 

The  indicator  used  is  usually  neutral,  bluish-violet  litmus  tinc- 
ture, which  is  added  to  the  liquid.  But  in  using  deeply-colored 
substances,  such  as  molasses,  the  indicator  is  not  added,  but  instead, 
after  each  addition  of  acid  the  liquid  is  tested  with  a  strip  of  bluish- 
violet,  sensitive  litmus  paper. 

(e)  Ash.  The  residue  left  on  ignition  of  a  sugar,  including  the 
mechanically  admixed  impurities  in  the  same,  is  called  the  "ash." 
The  residue  of  a  sugar  free  or  freed  from  these  impurities  is  called 
the  "salts."  The  latter  consists  mainly  of  alkali  sulphates  or 
chlorides  and  carbonates  arising  from  alkali  salts  of  organic  acids. 
Potassium  predominates  in  these  alkalies.  Sometimes  calcium  car- 
bonate, arising  from  soluble  organic  calcium  salts,  is  found. 
These  salts  hinder  crystallization  of  a  part  of  the  sugar  and  conse- 
quently cause  a  loss  in  the  yield  ;  and  furthermore,  even  though  this 
no  longer  holds  good  under  the  present  conditions,  one  part  salts 
is  calculated  to  yield  a  decrease  of  five  parts  sugar.  The  complete 
ignition  of  a  sugar  is  hard  to  accomplish  by  combustion,  since  the 
easily  fusible  alkali  salts  withhold  small  particles  of  carbon  from 
combustion.  Too  strong  a  heat  should  likewise  be  avoided  on 
account  of  possible  volatilization  of  alkali  chlorides.  The  inciner- 
ation is  therefore  conducted  as  follows  :  The  weighed  sugar  is  charred 
in  a  spacious  platinum  dish  until  gas  is  no  longer  evolved.  The  coke 
is  then  moistened  with  water  and  crushed  to  a  paste  with  a  pestle. 
After  the  addition  of  a  little  hot  water,  heating  and  filtering,  the 
residue  on  a  small  filter  is  repeatedly  washed  with  hot  water,  and 
the  filter  and  residue  together  are  incinerated  in  the  platinum  dish. 
The  filtrate  added  to  this  is  evaporated  to  dryness  on  a  water-bath, 
moistened  with  ammonium  carbonate,  dried  at  100°  and  moder- 
ately ignited.  The  clean  white  residue  is  weighed. 

In  this  manner  the  "ash"  (carbonate  ash)  is  ascertained.  If 
the  estimation  of  "  salts  "  also  be  desired,  a  weighed  quantity  of 
sugar  is  dissolved  in  water  (about  25  grs.  sugar  in  250  c.c).  The 
turbid  solution  is  filtered,  a  portion  of  the  filtrate  is  evaporated  in 
a  platinum  dish,  charred  and  heated  as  before. 

6 


82  CHEMICAL-TECHNICAL    ANALYSIS. 

Much  simpler  and  quicker  is  the  method  of  Scheibler.  3-5 
grs.  sugar  are  moistened  with  sulphuric  acid  in  a  platinum  dish. 
After  a  few  minutes  the  sugar  blackens  and  decomposes.  It  is  then 
heated  over  a  very  large  flame,  whereby  thorough  charring  takes 
place  with  much  swelling,  hissing  and  gas  evolution.  To  com- 
pletely burn  off  the  remaining  coke  the  dish  is  placed  in  a  muffle. 

The  action  of  the  sulphuric  acid  converts  the  salts  into  sulphates, 
the  weight  of  which  is  naturally  higher  than  that  of  the  salts  orig- 
inally present.  The  increase  of  weight  equals  almost  exactly  10 
per  cent. ,  by  which  the  amount  found  must  be  decreased.  The  re- 
mainder is  designated  as  sulphate  ash. 

(/)  Color.  The  Stammer  Colorimeter  is  used  for  this  purpose  ; 
however,  the  determination  is  rarely  carried  out.  The  crude  and 
refined  products  of  the  sugar  industry  which  are  subject  to  investi- 
gation are  beets,  beet  juice,  weak  juice,  dense  juice,  filling  material, 
green  syrup,  molasses,  osmosis  fluid  and  cane  sugar. 

1.  Beets. 

The  former  assumption,  that  the  sugar  content  in  the  juice  of  the 
beet  bears  a  fairly  constant  relation  to  that  of  the  beets  (about 
i  :  .95),  has  been  recently  proven  erroneous  for  different  reasons, 
and  therefore  methods  have  been  found  for  the  direct  determina- 
tion of  sugar  in  the  beet.  The  "  extraction  "  and  "  digestion" 
methods  are  recommended  for  this  purpose. 

(<z)  Extraction  method  (Scheibler).  An  exceedingly  fine  paste 
is  prepared  by  rasping  a  cross  section  of  the  beet  sample,  by  hand 
or  machine.  35-40  grs.  of  this  are  weighed  as  quickly  as  possible 
on  a  tared  pan  and  placed  in  the  cylinder  of  a  Soxhlet  extractor. 
In  the  wide  neck,  100  c.c.  flask,  with  which  the  apparatus  is  pro- 
vided, 75  c.c.  of  absolute  alcohol  are  placed.  The  residue  on  the 
pan  is  rinsed  into  the  cylinder  with  absolute  alcohol,  and  then  suf- 
ficient of  the  latter  is  added  to  fill  the  cylinder  almost  to  the  top 
of  its  siphon.  The  flask  is  attached  to  the  apparatus  and  heated 
until  extraction  is  complete.  This  as  a  rule  is  the  case  after  3-4 
hours,  in  which  time  the  alcohol  will  be  siphoned  80-90  times. 
The  water-bath  is  withdrawn,  the  flask  is  allowed  to  cool,  and  a 
sufficient  quantity  of  lead  acetate,  5—10  c.c.,  is  added.  It  is  then 
diluted  to  the  mark,  well  mixed  and  polarized  in  a  200  mm.  tube. 


BEETS.  83 

The  rotation  observed,  multiplied  by  .26048,  gives  the  amount  of 
sugar  contained  in  the  weighed  paste.  If  26.048  grams  of  beets 
are  used,  then  direct  percentages  of  sugar  are  obtained. 

(£)  Digestion  method  (Rapp  and  Degner).  Like  the  former, 
this  depends  on  an  alcohol  extraction,  the  difference  being  that 
52.1  grs.,  double  the  normal  weight  which  is  used,  are  directly 
placed  in  a  graduated  flask  of  exactly  200  c.c.  capacity.  The 
flask  is  marked  down  low  and  is  provided  with  a  widened  neck  into 
which  a  condenser,  about  50  cm.  in  length  and  10  mm.  diameter, 
can  be  ground  or  securely  fastened  with  a  tight-fitting  cork. 
Charging  in  is  done  with  a  glass  rod,  and  the  particles  adhering 
to  this,  to  the  pan  and  to  the  neck  of  the  flask,  are  washed  in  with 
a  wash-bottle  containing  90-92  per  cent,  alcohol.  The  flask  is 
filled  to  four-fifths  its  capacity  with  the  same  alcohol.  After  ad- 
justing the  condenser,  the  flask  is  placed  in  an  inclined  position  on 
a  water-bath  already  heated  to  boiling,  and  the  contents  of  the 
former  are  kept  in  ebullition  for  15-20  minutes.  The  sugar  is 
thereby  completely  dissolved  in  the  liquid.  The  flask  is  removed, 
the  condenser  washed  with  alcohol  and  filled  about  i  c.c.  above 
the  mark,  without  cooling.  By  successive  immersions  into  the  hot 
water-bath,  to  a  point  where  ebullition  begins,  a  thorough  mixture 
is  obtained.  It  is  thereupon  allowed  to  cool  in  the  air  for  ^-^  hour, 
and  is  finally  brought  to  the  temperature  of  the  room  by  immersing 
in  water.  To  the  liquid,  which  has  sunk  down  below  the  mark,  10- 
15  drops  of  lead  acetate  are  added.  It  is  then  diluted  to  the  mark 
with  alcohol,  well  mixed  by  shaking,  filtered  and  polarized.  The 
readings  made  with  the  use  of  a  200  mm.  tube  yield  direct  sugar  per- 
centage. In  order  to  compensate  for  the  extracted  pulp  left  in  the 
flask,  the  result  obtained  is  multiplied  by  .994.  The  true  percent- 
age is  thus  obtained.  Stammer  has  in  so  far  modified  the  opera- 
tion as  to  cover  an  unlimited,  usually  much  larger  quantity  of  the 
paste  with  strong  alcohol,  and  to  dilute  to  such  a  volume  that  direct 
percentage  of  sugar  in  the  beet  can  be  read  off  in  the  polariscope 
after  the  sugar  has  become  uniformly  admixed.  The  operation  re- 
quires particularly  fine  pulping  of  the  beet  paste  in  a  beet  cutting 
machine.  This  can  only  be  accomplished  in  specially  fitted  labor- 
atories. 


84  CHEMICAL-TECHNICAL    ANALYSIS. 

2.  Beet  Juice,  Thin  Juice. 

(#)  Specific  gravity.  The  estimation  is  made,  as  in  one  of  the 
previously  mentioned  methods,  preferably  with  Balling's  saccharom- 
eter,  in  which  case  the  corresponding  specific  gravity  is  referred  to 
in  the  tables.  The  temperature  required  is  17.5°. 

(£)  Sugar.  100  c.c.  juice  are  as  accurately  as  possible  placed  in 
a  flask  provided  with  a  second  mark  at  no  c.c.  It  is  filled  to  the 
latter  with  lead  acetate  and  is  frequently  shaken.  Clarification  and 
decolorization  are  effected  completely  after  a  few  moments.  In 
special  cases  where  this  quantity  of  lead  acetate  does  not  suffice, 
correspondingly  more,  about  one-fifth  volume  of  lead  acetate,  must 
be  added.  It  is  then  filtered  and  polarized  in  a  200  mm.  tube. 
The  angle  read  off  is  increased  by  one-tenth,  because  of  the  dilu- 
tion with  lead  acetate,  and  is  then  multiplied  by  .26048.  The 
volume  percentage — that  is  the  grams  sugar  in  100  c.c. — is  then 
obtained.  Should  the  per  cent,  by  weight  be  desired,  it  is  only 
necessary  to  divide  the  first  result  by  the  specific  gravity  obtained, 
according  to  (a).  Any  bubbles  which  arise  in  pouring  in  the  juice, 
and  which  are  difficult  to  remove,  are  preferably  depressed  by  the 
addition  of  a  few  drops  of  ether.  Adhering  liquid  on  the  sides  of 
the  neck  above  the  mark  is  removed  with  a  roll  of  filter  paper. 

3.  Raw  Sugar,  Filling  Material,  Green  Syrup,  Molasses. 

(#)  Sugar.  Qualitative  tests  must  be  made  for  invert  sugar 
prior  to  the  sugar  estimation.  This  is  done  by  clarifying  20  grs. 
substance,  dissolved  in  water,  with  lead  acetate  and  diluting  to  100 
c.c.  50  cc.  clear  filtrate  are  mixed  with  50  c.c.  Fehling's  solution 
(see  Reagents,  p.  90),  heated  on  a  wire  gauze  and  kept  boiling 
for  2  minutes.  Should  there  be  no  suboxide  of  copper  formed,  or 
at  most  an  inappreciable  amount,  the  presence  of  invert  sugar  is  not 
taken  into  account  and  the  estimation  proceeds  as  in  (a).  Should 
appreciable  quantities  of  invert  sugar  be  present,  the  estimation 
proceeds  as  in  (/?). 

(a)  Invert  sugar  is  not  present.  The  normal  weight  is  dissolved 
in  a  100  c.c.  graduated  flask  and  treated  with  2-3  c.c.  lead  acetate 
and  1-2  c.c.  alum  solution.  It  is  diluted  to  the  mark,  thoroughly 
shaken,  and  filtered.  The  clear  liquid  is  polarized  in  a  200  mm. 
tube.  This  gives  the  percentage  of  saccharose. 


RAW    SUGAR,    FILLING    MATERIAL,    GREEN    SYRUP,    ETC.       85 

Alumina  in  form  of  a  thin  hydrate  paste  is  substituted  for  lead 
acetate,  when  purer  sugars  are  used.  (See  Reagent,  p.  90.)  When 
lead  acetate  is  used  the  alkaline  reaction  may  be  neutralized  and 
the  slight  turbidity  destroyed  in  the  filtrate  by  introducing  a  glass 
rod  moistened  with  cone,  acetic  acid. 

(/?)  Invert  sugar  is  present.  The  operation  of  Clerget  is  used, 
especially  in  the  case  of  molasses. 

Half  the  normal  weight  (13.024  grs.)  is  dissolved,  with  addition 
of  75  c.c.  water,  in  a  100  c.c.  flask.  5  c.c.  hydrochloric  acid  sp.  gr. 
1.188  are  added.  The  flask  is  warmed  to  67—70°  in  a  water-bath 
heated  slightly  above  70°.  This  requires  2-3  minutes.  It  is  then 
kept,  while  shaking,  as  near  69°  as  possible  for  5  minutes.  It  is 
quickly  cooled,  filled  to  the  mark,  and  bone  black — or,  better, 
blood  charcoal — is  added,  when  necessary  to  decolorize.  It  is 
allowed  to  stand  for  a  few  minutes  and  is  then  polarized  as  near 
20°  as  possible.  The  result  is  doubled  when  a  200  mm.  tube  is  used. 
After  the  sugar  has  been  inverted  the  liquid  shows  a  strong  laevo- 
rotary  power  ( — 1°). 

In  addition  to  this  determination,  polarization  (a)  is  carried  out 
in  the  usual  manner  (-f-  P°). 

If  S  equal  the  sum  of  the  angle  before  and  after  the  inver- 
sion (omitting  the  negative  sign  of  the  invert  sugar),  therefore 
P  -f  1°,  and  t°  the  temperature  in  centigrade  degrees,  taken  at 
the  time  of  reading,  then  the  cane  sugar  R  can  be  calculated  from 
the  formula : 

R=^       IooS 

142.66 — y2 1°. 

This  formula  is  based  on  the  fact  that  pure  saccharose,  which  ro- 
tates 100°  before  inversion,  shows  after  inversion  a  rotation 

t° 
of  42.66 .     Therefore,     the     decrease    of   rotation    of  pure 

t° 
saccharose  =  142.66 —  —  . 

(^)  Invert  sugar.  When  the  presence  of  the  latter  is  detected 
according  to  (#),  the  approximate  amount  is  next  ascertained. 
10  grs.  substance,  dissolved  in  water,  are  clarified  with  lead  acetate 
and  diluted  to  100  c.c.  10,  8,  6,  4  and  2  c.c.  are  placed  in  sep- 
arate test  tubes,  5  c.c.  Fehling's  solution  are  added  to  each,  and 


86  CHEMICAL-TECHNICAL   ANALYSIS. 

the  contents  are  then  boiled.  Notice  is  now  taken  of  the  tube, 
whose  contents  are  nearly  decolorized.  Should  this  be  the  case 
with  the  one  containing  10  c.c.,  there  is  less  than  1.5  per  cent, 
invert  sugar  present,  and  the  determination  proceeds  according  to 
the  method  of  Herzfeld.  In  the  other  case  the  method  of  Meissl 
and  Hiller  is  used.  For  the  latter  method  the  number  of  c.c.  in 
that  test  tube  which  is  nearly  decolorized  give  simultaneously  the- 
number  of  grams  which,  dissolved  in  50  c.c.,  are  used  in  the  deter- 
mination. 

Every  c.c.  sugar  solution  (10  grs.  to  100  c.c.)  corresponds  to  .1 
gr.  substance.  But  in  the  method  of  Meissl  and  Hiller  ten  times 
the  amount  of  Fehling's  solution  (50  c.c.)  is  used.  Therefore,  ten 
times  the  quantity  of  sugar  is  also  taken.  Consequently,  every  c.c. 
solution  in  the  test  represents  i  gr.  substance  in  the  latter  deter- 
mination. 

Should  the  test  therefore  show  that  decolorization  took  place 
with  8  c.c.,  but  that  with  6  c.c.  a  blue  tint  remained,  then  6  grs. 
dissolved  in  50  c.c.  are  used. 

(a)  Method  of  Herzfeld.  A  solution,  clarified  with  lead  acetate, 
containing  the  normal  weight  in  100  c.c.,  is  used.  This  is  precipi- 
tated with  sodium  carbonate  when  any  great  excess  of  lead  acetate 
has  been  used  or  when  the  sample  is  rich  in  alkaline  earths. 

When  precipitation  with  soda  is  unnecessary  38.4  c.c.  filtered 
solution  diluted  to  50  c.c.  (=  10  grs.  substance)  are  used. 

When  previous  precipitation  is  necessary,  46.07  c.c.  solution, 
increased  to  60  c.c.  with  cone,  soda  solution,  are  withdrawn  and 
filtered.  50  c.c.  filtrate  are  then  taken,  and  these  also  correspond 
to  10  grs.  original  substance.  The  50  c.c.  are  placed  in  a  dish  or 
an  Erlenmeyer  flask  with  50  c.c.  Fehling's  solution,  and  are  heated 
to  boiling  for  3-4  minutes  over  a  wire  gauze  with  a  triple  burner. 
That  moment  is  accepted  as  the  beginning  of  ebullition  when  bub- 
bles arise  from  the  side  as  well  as  from  the  bottom  of  the  vessel. 
Boiling  is  continued  for  exactly  two  minutes  with  the  small  flame  of 
a  single  burner.  Thereupon  the  flask  or  dish  is  immediately  re- 
moved from  the  flame,  100  c.c.  cold  water  previously  boiled  are  added, 
and  the  contents  are  rapidly  filtered  with  the  aid  of  a  pump,  on  a 
weighed  asbestos  filter  (Fig.  8).  The  precipitate  is  rapidly  washed 
on  the  filter  with  the  aid  of  a  feather,  and  is  washed  subsequently 


RAW    SUGAR,    FILLING    MATERIAL,    GREEN    SYRUP,    ETC.       87 

with  300-400  c.c.  hot  water.  The  water  is  replaced  by  about 
20  c.c.  alcohol,  finally  with  ether,  and  the  tube  is  dried  in  an 
air-bath  at  120-130°.  The  portion  of  the  tube  containing  the 
cuprous  oxide  on  the  filter  is  next  heated  to  a  low 
red  heat  to  oxidize  and  destroy  organic  substances, 
and  is  then  reduced  by  heating  slowly  in  a  cur- 
rent of  hydrogen.  Reduction  is  complete  in  a 
few  minutes.  It  is  allowed  to  cool  in  hydrogen 
and  the  water  collected  in  the  neck  allowed  to 
evaporate.  It  is  then  placed  in  a  desiccator  and 
weighed  after  fifteen  minutes.  The  invert  sugar 
is  gotten  from  the  amount  of  reduced  .copper  by 
means  of  the  tables  (p.  89). 

The  following  details  are  yet  to  be  considered : 
The  asbestos  must  be  proof  against  alkalies  and  acids 
and  should  previously  be  ignited.  It  is  then  sus- 
pended in  water,  poured  on  the  glass  wool  in  the 
tube,  and  pressed  with  a  glass  rod  having  a  flattened 
end,  so  that  a  thin  but  perfectly  solid  layer,  which 
filters  without  use  of  pump,  is  formed.  It  is  then 
washed  with  alcohol  and  ether,  dried  and  weighed. 

During  filtration  a  short,  thick  funnel  is  loosely 
placed  on  the  tube.  While  washing,  however,  FlGt8< 

the  latter  is  replaced  by  a  funnel  attached  tightly  Asbestos'Filter- 
to  the  tube  by  means  of  a  rubber  stopper.  The  liquid  in  the  tube 
should  not  be  allowed  to  run  off  entirely.  The  hydrogen  used  in 
reducing  must  be  free  from  arsenic.  The  tube  is  attached  to  the 
hydrogen  generator  by  a  glass  tube  in  a  tightly-fitting  rubber 
stopper,  and  is  inclined  upwards  somewhat. 

Instead  of  an  asbestos  filter,  filter  paper  washed  with  hydro- 
fluoric acid  may  be  used.  In  this  case,  likewise,  300-400  c.c.  hot 
water  are  used  in  washing.  It  is  then  incinerated,  placed  in  a 
Rose  crucible,  covered  with  the  perforated  lid  and  reduced  in 
hydrogen.  When  the  quantity  of  cuprous  oxide  does  not  exceed 
.  i  gr.  it  may  be  converted  into  cupric  oxide  by  ignition  in  a  por- 
celain crucible,  weighed  as  such,  and  calculated  into  metallic 
copper. 

0     Method  of   Meissl   and    Hiller.     This   is   used   when   the 


88  CHEMICAL-TECHNICAL    ANALYSIS. 

amount  of  invert  sugar  exceeds  1.5  per  cent.  The  necessary  quan- 
tity of  substance  is  ascertained  from  the  previous  experiments.  In 
order  to  obtain  this  dissolved  in  50  c.c.,  double  the  quantity  is 
weighed  out,  brought  to  100  c.c.,  after  clarifying  with  lead  acetate, 
and  50  c.c.  of  the  filtrate  are  used.  With  this  quantity  the  deter- 
mination of  invert  sugar  is  conducted  exactly  as  in  the  Herzfeld 
method. 

In  order  to  use  the  following  tables  of  Meissl  and  Hiller  the  approxi- 
mate ratio  of  saccharose  to  invert  sugar  (R  :  I)  must  be  ascertained. 
The  method  of  calculation  is  apparent  from  the  following  consider- 
ations :  The  invert  sugar  can  be  assumed  to  be  equal  to  one-half  the 
copper  found.  If  p  grs.  substance  were  used  and  Cu  grs.  copper  were 
found,  then  there  were  contained  in  p  grs.  substance  approximately 

Cu 
ioo   — 

Cu                                                        2  _ 
—grs.  invert  sugar.  Therefore, —  i  grs.  invert  sugar  dissolved 

in  ioo  grs.  substance.  Furthermore,  had  the  determination  of 
cane  sugar  (a  /3  p.  85)  given  r  per  cent,  cane  sugar,  then  the  total 
saccharine  matter  =  r  -(-  i  per  cent.  To  determine  the  ratio  of 
saccharine  and  invert  sugar  in  ioo  parts  sugar,  the  invert  sugar  I  is 
next  calculated  from  the  proportion  (r  -f-  i)  :  i  =  ioo  :  I.  From 

this  I  = '—•  or,  after  substituting  the  values  previously  obtained: 

r  -f  i 


Cu 

IOO  .  IOO  

2 


I   = 


Cu 

p  .  r  -f  ioo  — 

The  saccharose  then  becomes  R  —  ioo  —  I.  The  ratio  R  :  I 
is  now  known,  and  the  factor  corresponding  to  this  ratio  and  to 
the  amount  of  invert  sugar  approximately  found  is  determined  on 
the  tables  (p.  90).  This  factor  F  substituted  in  the  equation  I'  = 

-  F  gives  I'  the  true  percentage  of  invert  sugar. 

(V)  Water  and  ash  are  determined  in  the  manner  previously  de- 
scribed. Sugar,  water  and  ash  added  together  and  deducted  from 
ioo  yields  the  non -saccharine  organic  matter. 

(rtQ  Alkalinity.     That  which  was  previously  stated  answers  in 


RAW    SUGAR,    FILLING    MATERIAL,    GREEN    SYRUP,    ETC.       89 


general  in  this  case.  When  molasses  is  used,  15-20  grs.  are  dis- 
solved and  diluted  to  250  c.c.  25-50  c.c.  of  this  solution  are 
placed  in  a  graduated  cylinder  and  1—2  c.c.  litmus  tincture  are 
added.  If  the  cylinder  be  held  horizontally  over  a  piece  of  white 
paper,  a  gray-green  color  is  observed  in  the  liquid  when  the  mo- 
lasses is  alkaline.  In  this  case  another  portion  is  titrated,  as  in  the 
method  already  mentioned. 

To  distinguish  whether  a  molasses  is  neutral,  the  contents  of  the 
cylinder  are  divided  into  two  parts.  To  one  part  one  drop  nor- 
mal acid  is  added,  to  the  other  a  drop  of  normal  alkali,  whereupon 
the  solutions,  if  originally  neutral,  should  become  either  red  or 
blue. 

(e)  Purity  quotient  is  the  sugar  contained  in  100  parts  actual  dry 
substance. 

(/)  "  Rendement ' '  or  Yield  is  the  number  which  designates 
how  much  crystallized  cane  sugar  is  capable  of  being  obtained 
from  a  raw  sugar.  The  customary  calculation  in  practice  funda- 
mentally assumes  5  parts  by  weight  ;  sugar  is  prevented  from 
crystallizing  by  i  part  by  weight  of  soluble  salts.  The  "  rende- 
ment ' '  in  Germany  and  England  is  therefore  obtained  by  deducting 
five  times  the  weight  of  salt  content  from  the  cane  sugar  content. 

The  assumption  is  a  rather  arbitrary  one. 

Tables  of  Herzfeld. 


Copper, 
mg. 

Invert 
Sugar. 
Per  Cent. 

Copper, 
mg. 

Invert 
Sugar. 
Per  Cent. 

Copper, 
mg. 

Invert 
Sugar. 
Per  Cent. 

Copper, 
mg. 

Invert 
Sugar. 
Per  Cent. 

50 

O.O5 

120 

0.40 

190 

0.79 

255 

.16 

55 

O.O7 

125 

0-43 

195 

0.82 

260 

.19 

60 

OOQ 

130 

0-45 

200 

0.85 

265 

.21 

65 

O.I  I 

135 

0.48 

205 

0.88 

270 

.24 

70 

0.14 

140 

0-51 

2IO 

0.90 

275 

•27 

75 

0.16 

H5 

0-53 

215 

0-93 

280 

•3° 

80 

0.19 

15° 

0.56 

220 

096 

285 

•33 

85 

0.21 

155 

0-59 

225 

0.99 

290 

.36 

90 

0.24 

1  60 

0.62 

230 

1.  02 

295 

.38 

95 

0.27 

I65 

0.65 

235 

1.05 

300 

.41 

100 

0.30 

170 

0.68 

240 

1.07 

305 

-44 

105 

0.32 

I7S 

0.71 

245 

1.  10 

3IO 

•47 

no 

0-35 

1  80 

0-74 

250 

1.13 

315 

•50 

"5 

038 

1  85 

0.76 

90 


CHEMICAL-TECHNICAL    ANALYSIS. 


Tables  of  Hiller. 


R:I. 

Cu 

2    =  200  mg. 

175  mg. 

150  mg. 

125  mg. 

ioo  mg. 

75  mg. 

50  mg. 

o  :  100 

56.4 

554 

54-5 

53-8 

532 

53° 

53-0 

10  :    90 

563 

55-3 

54-4 

53-8 

53-2 

52.9 

52.9 

20  :    80 

56.2 

55-2 

54-3 

53-7 

53-2 

52.7 

52.7 

30:    70 

56.1 

55-1 

54.2 

53-7 

53-2 

52.6 

52.6 

40  :    60 

55-9 

55-0 

54-i 

53-6 

53-1 

52.5 

52.4 

50:    50 

55-7 

54-9 

540 

53.5 

53-i 

52.3 

52.2 

60  :    40 

556 

54-7 

53-8 

53-2 

52-8 

52.1 

51.9 

70:    30 

55-5 

54-5 

53-5 

52*9 

52.5 

5L9 

51.6 

80  :    20 

55-4 

54-3 

53-3 

52.7 

52.2 

5J.7 

51.3 

90  :    10 

54.6 

53-6 

53  * 

52.6 

52.1 

5L6 

51.2 

91  :      9 

54.1 

53-6 

52.6 

52.i 

51.6 

51-2 

5°-7 

92  :      8 

53-6 

53-1 

52.1 

51.6 

51.2 

50-7 

50.3 

93:      7 

53-6 

53-1 

52.1 

512 

50.7 

5°  3 

49-8 

94:      6 

53» 

52.6 

5i.6 

50.7 

5°3 

49-8 

48.9 

95:      5 

52.6 

52.i 

5i.2 

50.3 

49-4 

48.9 

48.5 

96:     4 

52.1 

51-2 

50.7 

498 

48.9 

47-7 

46.9 

97'     3 

50-7 

50-3 

498 

48.9 

47-7 

46.2 

45-1 

98:      2 

49-9 

48.9 

4«-5 

47.2 

45-8 

433 

40.0 

99:      i 

47-7 

47-3 

46.5 

45-1 

43-3 

41.2 

38.i 

Keagents  Used  in  the  Methods  Described. 

1.  Lead  acetate.     600  grs.    sugar  of  lead  and  200  grs.  litharge 
are  covered  with  two  liters  of  water  and  allowed  to  stand,  with 
frequent  agitation,  for  twelve  hours  in  a  warm  place.     The  liquid 
is  filtered  from  the  sediment  and  placed  in  a  reagent  bottle.     The 
latter  is  best  provided  with  a  double-bored  stopper  in  which  are 
adjusted  a  siphon  and  a  soda-lime  tube. 

2.  Alumina.     Commercial  aluminium  chloride  is  dissolved  in  a 
flask  in  ioo  volumes  water  and  precipitated  with  ammonia  to  alka- 
line reaction.      The  precipitate  of  aluminium  hydrate  is  allowed  to 
settle,  the  supernatant  liquid  is  drawn  off,  and  the  precipitate  is 
washed  by  decantation  until  alkaline  reaction  ceases.     The  alumin- 
ium hydrate  so  prepared  is  preserved  as  a  thick  paste. 

3.  Fehling's  solution.     This  consists  of  the  two  following  solu- 
tions : 

(a)  34.639  grs.  crystallized  copper  sulphate  are  dissolved  in  500 
c.c.  water. 

(^)  I73  grs.  Seignette  salt  are  dissolved  in  400  c.c.  water,  ioo 
c.c.  sodium  hydrate  solution  containing  50  grs.  caustic  soda  are 


BONE    BLACK.  91 

added,  and  the  solution  is  filtered  if  necessary.  The  solutions  are 
kept  separate,  and  are  mixed  in  equal  volumes  prior  to  every  experi- 
ment. 

4.  Press  Cake. 

Sugar.  Portions  from  different  parts  of  the  press  'cake  under  in- 
vestigation are  selected,  ground  and  mixed,  and  of  this  uniform 
stiff  mass,  so  obtained,  the  normal  weight  is  taken.  This  quantity  is 
mixed  with  water,  placed  in  a  200  c.c.  flask  filled  to  the  mark  with 
a  little  lead  acetate  and  wash  water,  and  the  solution  is  polarized  in 
a  400  mm.  tube.  The  reading  gives  the  percentage  of  sugar.  The 
method  is  not  absolutely  exact,  but  suffices  for  technical  purposes. 
If  the  volume  occupied  by  the  calcium  carbonate  be  taken  into  con- 
sideration, 25  grs.  may  be  taken  instead  of  the  normal  weight,  and 
the  readings  still  considered  as  percentage. 

5.  Lime  Saccliarate. 

(a)  Sugar.  Half  the  usual  weight  is  placed  in  a  small  mortar 
and  ground  with  a  little  water  to  a  uniform  paste.  A  little  phenol- 
phthalein  is  added  as  indicator,  and  cone,  acetic  acid  is  added  while 
the  particles  are  crushed,  and  the  solution  is  stirred  until  the  red  color 
disappears.  When  the  decomposition  is  complete  the  solution  is 
washed  into  a  100  c.c.  flask,  a  small  amount  of  lead  acetate  is 
added,  and  the  whole  is  diluted  to  the  mark.  It  is  then  filtered  and 
polarized.  When  a  200  mm.  tube  is  used  the  reading  is  doubled,  in 
order  to  obtain  per  cent,  units. 

(^)  Lime.  2-5  grs.  are  weighed,  ground  in  a  mortar  and 
titrated  with  normal  or  half-normal  acid,  using  phenol-phthalein 
as  an  indicator.  The  result  is  expressed  in  lime  units. 

6.  Bone  Black. 

This  substance  serves  as  a  decolorizer  whose  use  in  sugar  factories 
is  undoubtedly  diminishing.  The  investigation  includes  water,  car- 
bon, sand,  clay,  carbonate  of  lime,  sulphate  of  lime,  calcium  sul- 
phide and  phosphoric  acid. 

(a}  Water.  A  weighed  quantity,  about  10  grs.  sample,  used  in 
form  of  a  coarse  powder,  is  dried  to  constant  weight,  at  140-150° 
in  a  well-ground,  stoppered  weighing-bottle. 

(Y?)  Carbon,  sand  and  clay.     For  this  purpose,  as  in  the  follow- 


92  CHEMICAL-TECHNICAL    ANALYSIS. 

ing,  the  finely-powdered  and  air-dried  bone  black  is  used,  and  since 
the  water  is  different  in  this  sample  from  that  in  the  former,  a  sep- 
arate water  determination  is  made.  The  results  are  reckoned  as 
anhydrous  bone  black. 

The  operation  is  conducted  as  follows :  10  grs.  substance  are 
moistened  with  water.  50  c.c.  hydrochloric  acid  are  carefully 
added,  and  the  mixture  is  heated  to  boiling  for  ^  hour.  It  is 
then  filtered  through  a  dried  and  weighed  filter  and  washed  with 
hot  water  until  acidity  ceases.  The  filtrate  (A~)  is  collected  in  a 
liter  flask.  The  filter  and  residue  are  dried  to  constant  weight. 
The  increase  in  weight  represents  carbon  -f  sand  -f  clay.  Filter 
and  residue  are  now  ignited.  Sand  and  clay  remain.  The  carbon 
is  calculated  from  the  difference  between  this  and  the  former 
weight. 

(V)  Carbonate  of  lime.  The  Scheibler  apparatus  (Fig.  9)  is 
almost  exclusively  used  for  this  purpose. 

The  generation  of  carbonic  acid  takes  place  in  flask  A,  in 
which  the  finely -powdered  substance  is  placed  and  allowed  to  come 
in  contact  with  the  hydrochloric  acid  in  the  gutta-percha  cylinder 
S.  The  carbonic  acid  evolved  passes  through  the  glass  tube,  which 
is  sealed  in  the  stopper,  and  then  through  the  rubber  tube  r  into  a 
thin  rubber  balloon,  X,  contained  in  the  flask  B.  Besides  the  con- 
nection with  A,  the  flask  B  is  connected,  by  means  of  the  glass 
tube  uu,  with  the  graduated  tube  C,  and  finally  with  a  third,  which 
communicates  with  the  outer  air.  This  may  be  established  or  pre- 
vented by  the  pinchcock  q. 

The  eudiometer  C,  divided  into  25  c.c.,  communicates  below 
with  the  tube  Z>,  whose  lower  end  is  provided  with  an  exit  tube 
which  extends  to  the  floor  of  the  two-neck  flask  E.  Pinchcock  p 
is  placed  on  a  piece  of  rubber  tubing  between  D  and  E.  By  forc- 
ing air  into  flask  E,  preferably  with  an  elastic  ball,  the  water  pres- 
ent in  E  can  be  forced  into  C  and  D.  On  the  other  hand,  by 
opening  the  pinchcock/  it  may  be  let  out  of  Cand  D  into  E. 

Operation, — The  normal  weight  (1.7  grs.)  required  by  the  appa- 
ratus of  the  finely -powdered  bone  black  is  weighed  out  and  placed 
in  the  thoroughly  dried  flask  A.  The  gutta-percha  vessel  S  is  then 
filled  with  hydrochloric  acid  of  1.12  density  (2  vols.  cone,  hydro- 
chloric acid,  i  vol.  water)  and  carefully  placed,  with  forceps,  in  A, 
so  that  it  rests  on  the  glass  side  in  a  slanting  position. 


BONE    BLACK. 


93 


After  raising  the  water  in  C  to  the  zero  mark  by  forcing  air  into 
the  flask  E  and  simultaneously  opening  the  clip  /,  A  is  closed  with 
the  well-greased  stopper. 


FIG.  9. — Scheibler's  Apparatus. 

Any  air  pressure  and  consequent  change  in  the  level  of  the  liquid 
in  C  and  D  are  removed  by  opening  the  clip  q  once.  The  vessel 
A  is  taken  between  thumb  and  middle  finger  of  the  right  hand, 


94  CHEMICAL-TECHNICAL    ANALYSIS. 

while  the  forefinger  presses  the  stopper.  The  flask  is  then  inclined 
sufficiently  to  allow  the  acid  to  escape  from  the  gutta-percha  holder. 
Decomposition,  which  ensues,  is  sustained  and  augmented  by  care- 
ful continued  shaking  of  the  flask  A.  Simultaneously  the  clip/  is 
opened  with  the  left  hand,  and  as  much  water  is  allowed  to  flow  into 
E  as  is  necessary  to  bring  both  levels  in  tubes  C  and  D  to  about 
the  same  height ;  that  in  D  somewhat  higher  than  in  C. 

When  water  in  C  ceases  to  descend  on  prolonged  agitation  of  A, 
the  decomposition  is  complete.  5-10  minutes  are  allowed  to  elapse 
in  order  to  allow  pressure  and  temperature  to  equalize,  after  which 
the  levels  in  C  and  D  are  brought  to  the  same  height  by  carefully 
opening  the  clip  q. 

The  level  in  C  is  read  off,  as  well  as  the  temperature  of  a  ther- 
mometer placed  in  the  apparatus.  The  direct  percentage  of  car- 
bonate of  lime  is  found,  by  means  of  these  two  numbers,  on  the  ac- 
companying tables  calculated  by  Scheibler. 

(</)  Sulphate  of  lime.  500  c.c.  of  the  filtrate  A  (see  &)  are 
nearly  neutralized  with  sodium  carbonate,  concentrated  by  evapora- 
tion and  precipitated  with  barium  chloride.  The  sulphuric  acid 
obtained  is  calculated  into  calcium  sulphate, 

(<?)  Calcium  sulphide.  About  10  grs.  finely-powdered  bone 
black  are  dissolved  in  fuming  nitric  acid  or  hydrochloric  acid  and 
potassium  chlorate.  The  liquid  is  filtered.  The  filtrate  is  diluted 
to  500  c.c. ,  and  the  sulphuric  acid  in  250  c.c.  is  determined  as 
before.  The  sulphuric  acid  found  in  (V),  deducted  from  that  just 
found,  gives  the  sulphuric  acid  corresponding  to  the  sulphur  of  the 
calcium  sulphide,  from  which  the  latter  is  readily  calculated. 

(/)  Phosphoric  acid.  This  determination  is  minutely  described 
in  the  chapter  on  Fertilizers.  It  is  of  special  importance  in  bone- 
black  waste. 


VII,  Fermentation  Industries. 


IN  this  chapter  the  investigation  of  raw  products  containing 
starch,  malt,  yeast  and  spirits,  will  be  discussed. 

1.  Raw  Products  Containing-  Starch. 

The  most  important  determinations  required  are  starch  and  total 
nitrogen. 

(0)  Starch.  Two  methods  are  in  use,  in  connection  with  the 
methods  of  solution  used  in  practice.  The  one  is  conducted  with 
high  pressure,  the  other  without.  The  starch,  dissolved  in  either 
one  or  the  other  way,  is  eventually  inverted  and  calculated  from  the 
dextrose  formed. 

(«)  Method  of  Reinke,  with  use  of  high  pressure.  The  finely- 
divided  substance  is  used  in  form  of  a  flour,  in  a  separate  portion 
of  which  the  water  has  been  determined.  In  addition,  the  water  in 
the  original  substance  must  be  ascertained.  The  values  found  for 
the  flour  are  recalculated  on  this. 

Three  grs.  flour  are  moistened  in  a  metal  or  glass  beaker  with  25 
c.c.  i  per  cent,  solution  of  lactic  acid  and  30  c.c.  water.  The 
mass  is  covered  with  a  watch  crystal  and  heated  for  2^  hours  at  3^ 
atmospheres  in  a  Soxhlet  steam -kettle,  or,  in  the  absence  of  the 
latter,  in  a  Lintner  pressure -flask.  After  cooling,  50  c.c.  hot 
water  are  added.  The  solution  is  then  placed  in  a  250  c.c.  flask 
and  diluted  to  the  mark.  After  occasional  shaking,  during  a  period 
of  a  half  hour's  standing,  the  solution  is  filtered. 

200  c.c.  of  the  filtrate,  to  which  15  c.c.  hydrochloric  acid  (sp. 
gr.  1.125)  have  been  added,  are  briskly  boiled  on  a  reflux  conden- 
ser for  two  hours.  Upon  cooling,  the  liquid  is  neutralized  with 
caustic  soda  to  faint  acid  reaction  and  diluted  to  500  c.c.  In  order 
to  know  once  and  for  all  how  much  alkali  to  add,  15  c.c.  hydro- 
chloric acid  (1.125)  are  titrated  with  the  former.  The  quantity 


96 


CHEMICAL-TECHNICAL    ANALYSIS. 


Determination  of  Grape-Sugar  {Dextrose}.     F.  Allihn. 


Copper. 
mg. 

Dex- 
trose, 
mg. 

Copper, 
mg. 

Dex- 
trose, 
mg. 

Copper, 
mg. 

Dex- 
trose. 

mg. 

Copper, 
mg. 

Dex- 
trose, 
mg. 

Copper, 
mg. 

Dextrose, 
mg. 

IO 

6.1 

56 

28.8 

I  O2 

5L9 

148 

75-5 

194 

99-4 

II 

6.6 

57 

293 

I03 

52.4 

149 

76.0 

195 

1  00.0 

12 

7-1 

58 

298 

I04 

52.9 

150 

76.5 

196 

100.5 

13 

7.6 

•59 

30-3 

105 

535 

151 

77.0 

I97 

IOI.O 

H 

8.1 

60 

30.8 

1  06 

54-0 

152 

77-5 

198 

101.5 

15 

8.6 

61 

31.3 

107 

54-5 

153 

78.1 

199 

I02.O 

16 

9.0 

62 

31.8 

108 

55-0 

154 

78.6 

200 

1  02.  6 

17 

9-5 

63 

32.3 

109 

55-5 

155 

79.1 

2O  I 

103.2 

18 

IO.O 

64 

32.8 

no 

56.0 

I56 

796 

2O2 

103.7 

19 

10.5 

65 

33-3 

III 

56-5 

157 

80.1 

203 

104.2 

20 

II.O 

66 

33-8 

112 

57-0 

158 

80.7 

2O4 

104.7 

21 

"•5 

67 

34-3 

"3 

57-5 

159 

81.2 

205 

105.3 

22 

I2-O 

68 

34-8 

114 

58.0 

1  60 

8i.7 

2O6 

105.8 

23 

12-5 

69 

353 

H5 

58.6 

161 

82.2 

2O7 

106.3 

24 

13.0 

70 

35-8 

116 

59.i 

162 

82.7 

208 

106.8 

25 

'3-5 

71 

36.3 

117 

59-6 

163 

83.3 

2O9 

107.4 

26 

14.0 

72 

36.8 

118 

60.  i 

164 

83.8 

210 

107.9 

27 

14-5 

73 

37-3 

119 

60.6 

165 

84.3 

211 

108.4 

28 

15.0 

74 

37-8 

1  20 

61.1 

1  66 

84.8 

212 

109.0 

29 

15-5 

75 

383 

121 

61.6 

167 

85.3 

213 

109.5 

3° 

1  6.0 

76 

38.8 

122 

62.1 

1  68 

85.9 

214 

I  IO.O 

3i 

16.5 

77 

39.3 

I23 

62.6 

169 

86.4 

215 

110.6 

32 

17.0 

78 

39-8 

124 

63-1 

170 

86.9 

216 

in.  i 

33 

'7-5 

79 

403 

125 

63.7 

171 

87.4 

217 

U  1.6 

34 

1  8.0 

80 

40.8 

126 

64.2 

172 

879 

218 

II2.I 

35 

18.5 

81 

4i.3 

127 

64.7 

173 

88.5 

219 

1127 

36 

18.9 

82 

41.8 

128 

65.2 

174 

89.0 

22O 

II3.2 

37 

19.4 

83 

42.3 

129 

65.7 

175 

89-5 

221 

II3.7 

38 

19.9 

84 

42.8 

130 

66.2 

176 

90.0 

222 

II4-3 

39 

20.4 

85 

43-4 

J31 

66.7 

177 

9°-5 

223 

II4.8 

40 

20.9 

86 

43-9 

132 

67.2 

178 

91  i 

224 

II5-3 

4i 

21.4 

87 

44-4 

!33 

67.7 

179 

91.6 

225 

"5-9 

42 

21.9 

88 

449 

134 

68.2 

1  80 

92.1 

226 

116.4 

43 

22.4 

89 

45-4 

135 

68.8 

181 

926 

227 

116.9 

44 

22.9 

90 

45-9 

136 

69-3 

182 

93-1 

228 

117.4 

45 

23-4 

9i 

46.4 

137 

69.8 

183 

93-7 

229 

118.0 

46 

23-9 

92 

46.9 

138 

70.3 

184 

94-2 

230 

118.5 

47 

24.4 

93 

474 

*39 

708 

185 

94-7 

231 

1190 

48 

24.9 

94 

47-9 

140 

7L3 

1  86 

95-2 

232 

119.6 

49 

254 

95 

48.4 

141 

71.8 

187 

95-7 

233 

1  20.  1 

50 

25-9 

96 

48.9 

142 

72.3 

188 

96.3 

234 

120.7 

51 

26.4 

97 

49-4 

H3 

72.9 

189 

96.8 

235 

121.  2 

52 

26.9 

98 

49-9 

144 

734 

190 

97-3 

236 

121.7 

53 

27.4 

99 

5°-4 

H5 

73-9 

191 

97-8 

237 

122.3 

54 

27.9 

100 

50.9 

146 

74-4 

192 

98.4 

238 

122.8 

55 

28.4 

IOI 

51.4 

147 

74-9 

193 

98.9 

239 

1234 

added  is  then  made  less  than  that  required  to  fully  neutralize.    The 
dextrose  is  determined  with  Fehling's  solution  in  50  c.c.  of  neu- 


RAW    PRODUCTS    CONTAINING   STARCH. 


97 


Determination  of  Grape-Sugar  {Dextrose} .    F.  Allihn* — Continued* 


Copper, 
mg. 

Dex- 
trose, 
mg. 

Copper, 
mg. 

Dex- 
trose, 
mg. 

Copper, 
mg. 

Dex- 
trose, 
mg. 

Copper, 
mg. 

Dex- 
trose, 
mg. 

Copper, 
mg. 

Dextrose, 
mg. 

240 

123.9 

285 

148.3 

330 

I73.I 

375 

198.6 

420 

224.5 

241 

124.4 

286 

148.8 

331 

173-7 

376 

199.1 

421 

225.1 

242 

125.0 

287 

149.4 

332 

174.2 

377 

199.7 

422 

225.7 

243 

125.5 

288 

149.9 

333 

174.8 

378 

200.3 

423 

226.3 

244 

I26.O 

289 

150.5 

334 

175-3 

379 

200.8 

424 

226.9 

245 

126.6 

290 

151.0 

335 

175.9 

380 

201.4 

425 

227.5 

246 

I27.I 

291 

151.6 

336 

176.5 

38i 

2O2.O 

426 

228.0 

247 

127.6 

292 

152.1 

337 

177.0 

382 

202-5 

427 

228.6 

248 

I28.I 

293 

152.7 

338 

177.6 

383 

203.1 

428 

229.2 

249 

128.7 

294 

153-2 

339 

I78.I 

384 

203.7 

429 

229.8 

250 

129.2 

295 

153.8 

340 

178.7 

385 

204.3 

430 

230.4 

251 

129.7 

296 

154.3 

34i 

179.3 

386 

204.8 

431 

231.0 

252 

I30.3 

297 

154.9 

342 

179.8 

387 

205.4 

432 

231.6 

253 

I30.8 

298 

155.4 

343 

180.4 

388 

2O6.O 

433 

232.2 

254 

I3M 

299 

156.0 

344 

180.9 

389 

206.5 

434 

232.8 

255 

I3L9 

300 

156.5 

345 

181.5 

390 

2O7.I 

435 

233-4 

256 

I324 

3OI 

I57-I 

346 

I82.I 

39i 

207.7 

436 

233-9 

257 

^33-0 

302 

157.6 

347 

182.6 

392 

208.3 

437 

234-5 

258 

133-5 

303 

158.2 

348 

183.2 

393 

2088 

438 

235.1 

259 

I34.I 

3°4 

158.7 

349 

183.7 

394 

209.4 

439 

2357 

260 

134.6 

3°5 

159-3 

35° 

1843 

395 

2IOO 

440 

236.3 

26l 

I35-I 

306 

159.8 

351 

184.9 

396 

2IO.6 

441 

236.9 

262 

135.7 

3°7 

160.4 

352 

1854 

397 

2II.2 

442 

237-5 

263 

136.2 

308 

160.9 

353 

186.0 

398 

2II.7 

443 

238.1 

264 

136.8 

309 

161.5 

354 

186.6 

399 

212.3 

444 

238.7 

265 

137.3 

310 

162.0 

355 

187.2 

400 

212.9 

445 

239-3 

266 

137.8 

311 

162.6 

356 

l877 

401 

213.5 

446 

239.8 

267 

138.4 

312 

163.1 

357 

188.3 

402 

2I4.I 

447 

240.4 

268 

138.9 

313 

163.7 

358 

188.9 

403 

214.6 

448 

241.0 

269 

139.5 

3'4 

164.2 

359 

189.4 

404 

215.2 

449 

241.6 

270 

1400 

315 

164.8 

360 

190.0 

405 

215.8 

450 

242.2 

27I 

140.6 

3i6 

165.3 

361 

190.6 

406 

216.4 

45  ! 

242.8 

272 

141.1 

317 

165.9 

'362 

I9I.I 

407 

217.0 

452 

243.4 

273 

141.7 

3i8 

166.4 

363 

I9I.7 

408 

217-5 

453 

244.0 

274 

142.2 

319 

167.0 

364 

192.3 

409 

218.1 

454 

244.6 

275 

1428 

320 

167-5 

365 

192.9 

410 

2l8j 

455 

245-2 

276 

H3-3 

321 

I68.I 

366 

193.4 

411 

219.3 

456 

2457 

277 

143-9 

322 

168.6 

367 

194.0 

412 

219.9 

457 

246.3 

278 

144.4 

323 

169.2 

368 

194.6 

413 

220.4 

458 

246.9 

279 

I45.o 

324 

169.7 

369 

I95-I 

414 

22I.O 

459 

247.5 

280 

1455 

325 

170-3 

370 

195-7 

415 

221.6 

460 

248.1 

28l 

146.1 

326 

170.9 

37i 

196.3 

416 

222.2 

461 

248.7 

282 

146.6 

327 

171.4 

372 

196.8 

417 

222.8 

462 

249.3 

283 

147.2 

328 

172.0 

373 

197.4 

418 

223.3 

463 

249.9 

284 

147.7 

329 

172.5 

374 

198.0 

419 

2239 

tralized  solution,  corresponding  to  .  24  gr.  substance.    For  this  pur- 
pose, according  to  Allihn,  30  c.c.  copper  sulphate  solution  and  30 

7 


98  CHEMICAL-TECHNICAL    ANALYSIS. 

c.c.  alkaline  Seignette  solution  are  diluted  in  a  porcelain  dish  of 
200  c.c.  capacity  with  sufficient  water  to  bring  the  total  volume, 
after  adding  the  sugar  solution  under  examination,  to  145  c.c. — in 
this  instance  35  c.c.  This  solution  is  boiled.  50  c.c.  dextrose 
solution  are  run  into  the  boiling  liquid,  which  is  held  in  ebullition 
for  two  minutes  from  the  moment  that  boiling  again  sets  in. 

Further  treatment  is  conducted  in  exactly  the  same  manner  as 
described  in  the  determination  of  invert  sugar.  In  the  accompany- 
ing tables  of  Allihn  are  found  the  values  for  dextrose  corresponding 
to  the  copper  obtained.  To  calculate  into  starch,  the  quantity  of 
dextrose  is  multiplied  by  .9. 

The  method  is  applied  mainly  to  the  determination  of  starch  in 
potatoes. 

(/?)   Method  of  Marcker,  without  the  use  of  high  pressure. 

Solution  of  the  starch  is  here  accomplished  by  diastase.  3  grs. 
substance,  previously  extracted  in  a  Soxhlet  apparatus  with  ether, 
if  necessary,  to  free  from  fat,  are  boiled  with  looc.c.  water  for  ^ 
hour  on  a  reflux  condenser.  The  solution  is  cooled  to  65°  and  10 
c.c.  malt  extract  (prepared  according  to  directions  given  below) 
are  added.  The  solution  is  kept  at  65°  for  ^  hour.  Thereupon 
the  solution  is  again  boiled  for  ^  hour,  again  cooled  to  65°,  and 
allowed  to  remain  at  this  temperature  for  ^  hour  after  addition  of 
another  10  c.c.  malt  extract.  Finally  it  is  boiled,  cooled,  diluted 
to  200  c.c.  and  filtered.  200  c.c.  filtrate  are  inverted  with  15  c.c. 
hydrochloric  acid  (1.125),  then  neutralized  and  diluted  to  500  c.c. 

50  c.c.  are  reduced  with  Fehling's  solution.  The  remaining 
operation  is  conducted  precisely  as  in  (a). 

From  the  dextrose  values  found  in  the  tables,  that  amount  is  to  be 
deducted,  which  corresponds  to  1.6  c.c.  malt  extract  contained  in 
50  c.c.  The  difference  multiplied  by  .9  gives  the  starch  in  .24  gr. 
flour. 

Preparation  of  malt  extract. — 100  grs.  bruised  kiln -dried  malt 
are  covered  with  i  L.  water  and  macerated,  with  occasional  agita- 
tion, for  a  period  of  6  hours.  It  is  thereupon  filtered.  The  filtrate 
keeps  better  on  addition  of  a  little  chloroform. 

Dextrose  value  of  the  malt  extract. — 50  c.c.  are  diluted  with  150 
c.c.  water  and  boiled  on  a  reflux  condenser  in  a  flask  with  15  c.c. 
hydrochloric  acid  (1.125)  for  two  hours.  It  is  then  nearly  neu- 


STARCH.  99 

tralized,  diluted  to  500  c.c.,  and  50  c.c.  treated,  as  heretofore,  with 
Fehling's  solution.  The  dextrose  value,  corresponding  to  the  cop- 
per found,  multiplied  by  .32,  gives  the  amount  of  dextrose  corres- 
ponding to  1.6  c.c.  malt  extract,  which  is  to  be  deducted. 

(<£)  Total  nitrogen.  The  determination  is  conducted  according 
to  the  method  of  Kjeldahl,  in  precisely  the  same  manner  as  under 
Nitrogen  Fertilizers  (p.  78).  i  gr.  substance  is  used.  By  multi- 
plying the  nitrogen  found  by  6.25  the  crude  proteids  are  obtained. 

2.  Starch. 

The  investigation  includes  chiefly  the  determination  of  water, 
the  detection  of  impurities  and  adulterants,  as  well  as  establishing 
the  raw  product  from  which  it  was  made. 

For  the  latter  purpose  use  is  made  chiefly  of  the  microscopic 
method  of  investigation,  which,  however,  will  not  be  further  de- 
scribed here.*  A  starch  determination  can  be  conducted  by  in- 
verting 2.5—3  grs.  substance  by  boiling  with  200  c.c.  water  and 
20  c.c.  hydrochloric  acid  (1.125)  for  three  hours.  The  dextrose 
formed  is  determined  with  Fehling's  solution,  as  before.  Accord- 
ing to  Sachsse,  100  grs.  dextrose  equal  91.67  grs.  starch.  The 
operation  is  seldom  conducted. 

(a)  Water.  About  10  grs.  starch  are  weighed  out,  dried  at  first 
for  an  hour  at  40-50°,  and  then  for  3-4  hours  to  constant  weight 
at  120°  C. 

(^)  Impurities  and  adulterants.  These  may  be  both  organic 
and  inorganic  in  nature  : 

(a)  Inorganic  matter.  This  is  ascertained  from  the  amount  of 
ash  present,  and  is  estimated  by  an  ash  determination.  Mineral 
adulteration  is  usually  done  with  sand,  gypsum,  chalk,  heavy  spar 
and  clay. 

(/?)  Organic.  The  starch  is  dissolved  with  malt  extract  and  the 
residue  is  examined.  It  contains  such  organic  impurities  as 
wood  particles,  fibres,  coal-dust,  chaff,  fungus  spores,  etc.  Organic 
adulterants  can  hardly  be  else  than  cheaper  grades  of  starch 
which  are  added  to  the  finer,  and  which  are  determined  micro- 
scopically. 

*  An  excellent  reference  is  the  small  book  of  V.  Hohnel,  "  Starch  and  Ground 
Products." 


100  CHEMICAL-TECHNICAL    ANALYSIS. 

3.  Malt. 

For  this  investigation  the  combined  method  of  E.  Jalowetz,  pre- 
pared at  the  Congress  of  Agriculture  and  Forestry  in  Vienna,  1890, 
will  be  discussed. 

(#)  Water.  4—5  grs.  malt  are  weighed  off  in  form  of  whole 
grains  and  are  bruised  as  nearly  quantitatively  as  possible  in  a  special 
mill.  The  substance,  which  is  placed  in  watch  crystals  provided 
with  clasps,  is  heated  in  an  atmosphere  of  dry  hydrogen  in  a  drum- 
shaped  water-bath.  If  the  latter  is  inaccessible,  it  is  dried  in  a 
well -ventilated  air-bath  at  98-104°.  In  the  first  case  drying  re- 
quires 6  hours  ;  in  the  latter,  3-4  hours.  It  is  finished  when  the 
loss  in  weight  no  longer  exceeds  .25  per  cent. 

Very  moist  malt  is  dried  at  40-50°. 

(<£)  Extract.  50  grs.  whole  malt  are  weighed  out  and  ground, 
without  loss,  in  a  malt  mill.  It  is  then  washed  with  about  200  c.c. 
water  of  45°  C.  temperature,  in  a  weighed  beaker  of  about  500  c.c. 
capacity,  and  is  kept  in  a  water-bath  at  the  same  temperature  for  a 
half  hour.  The  temperature  of  the  bath  is  thereupon  increased  i  ° 
from  minute  to  minute,  so  that  after  a  period  of  25  minutes  a  tem- 
perature of  70°  is  reached.  The  mash  is  kept  at  this  temperature 
until  saccharizing  is  complete,  which  is  usually  the  case  in  about 
y2  hour.  The  end  reaction  is  ascertained  by  means  of  iodine  tests 
which  are  calculated  in  this  manner  :  A  drop  of  mash  is  placed  on 
a  porcelain  dish.  A  drop  of  iodine  solution  is  added  and  allowed 
to  stand  for  a  while.  The  first  test  is  made  10  minutes  after 
saccharizing  has  begun  ;  that  is,  after  the  mash  has  attained  a  tem- 
perature of  70°.  Further  tests  are  made  at  intervals  of  5—10  min- 
utes. Saccharizing  is  considered  finished  when  the  iodine  tests 
show  a  weak  red  or  a  pure  yellow  color.  The  time  consumed,  up 
to  this  moment,  is  named  the  * '  time  of  saccharizing. ' '  The  mash 
is  now  removed  from  the  water-bath,  cooled,  and  treated  with 
approximately  200  c.c.  cold  water.  On  the  balance,  the  weight  of 
the  mash  is  increased  by  addition  of  water  to  450  grs.  It  is  mixed 
and  filtered  into  a  dry  flask  through  a  ribbed  filter.  The  filter  should 
be  capable  of  receiving  the  entire  quantity  of  mash  at  once.  The 
first  portion  of  about  100  c.c.  is  replaced  in  the  filter  and  the 
density  of  the  subsequent  filtrate  is  determined  with  a  pyknometer. 
The  latter,  filled  with  the  wort,  should  stand  about  one  hour  in  a 


MALT.  101 

bath  at  17.5°.  By  means  of  the  density,  the  corresponding  ex- 
tract e,  that  is,  the  extractive  matter  in  100  c.c,  is  sought  for  in 
Balling's  tables. 

The  extract  E  of  the  air-dried  malt  is  found  by  means  of  the 

W         E 

formula  (100 — e)  :  e  —  (400  -| )  :      -  where   W    equals    the 

amount  of  water  expressed  in  per  cent. 
It  then  becomes  : 

e  (400  +  ^ 

E=2.  — 2- 

ioo  —  e 

In  ioo  parts  by  weight  of  wort  there  are  e  parts  extract,  and  ioo — 
E  parts  water.  The  total  weight  of  the  mash  equaled  450  grs. ,  /.  e.  ,400 

W 
grs.  water  and  50  grs.  malt,  with  Wfi  water,  hence  in  all  400  -f  — 

grs.  water.  If  the  percentage  of  extract  in  the  malt  equal  E,  then  in 
50  grs.  malt  there  are  contained  —  grs.  extract.  The  previously  con- 
structed proportion  is  hereby  sufficiently  explained. 

{c)  Maltose.  The  estimation  of  maltose  is  conducted  gravi- 
metrically  by  reduction  with  Fehling's  solution. 

30  c.c.  of  the  wort  obtained  as  in  (b}  are  diluted  to  200  c.c.  25 
c.c.  of  the  dilute  solution  are  run  into  50  c.c,  boiling  Fehling's 
solution.  It  is  kept  boiling  for  4  minutes,  the  suboxide  of  copper 
is  filtered  through  an  asbestos  filter,  and  the  remaining  operation  is 
conducted  as  heretofore.  The  maltose  corresponding  to  the  copper 
found  is  determined  from  the  tables  of  Wein  (see  page  102). 

Let  the  maltose  be  m,  then  the  original  30  c.c.  wort  contain  8m 
grams  maltose.  Furthermore,  if  the  extract  in  ioo  grs.  be  e,  then 
the  extract  in  30  c.c.  or  30  d  grams  (d=density)  =  .3  .  d  .  e.  In 
order  to  find  the  maltose  M  in  E  grs.  extract,  use  is  made  of  the  pro- 
portion : 

.3.  d.  e:  SmrzrE:  M. 

Therefore  the  percentage  of  maltose  is 

8m  E 

-rjTarr 

(d}  Diastatic  value.  The  estimation  depends  on  the  fact  that 
a  malt  extract  of  known  value  inverts  more  starch  the  higher  its 


102 


CHEMICAL-TECHNICAL    ANALYSIS. 


Weirf  s  Tables  for  the  Determination  of  Maltose. 


Copper, 
nig. 

Maltose, 
nig. 

Copper. 
mg. 

Maltose, 
mg. 

30 

25-3 

170 

149-4 

40 

33-9 

1  80 

158.3 

50 

42.6 

I90 

167.2 

60 

51-3 

2OO 

I76.I 

70 

60.  1 

2IO 

185.0 

80 

689 

220 

193-9 

90 
100 

Hi 

230 
24O 

202.9 
2II.8 

1  10 

95-5 

250 

220.8 

120 

104.4 

260 

229.8 

I30 

"34 

270 

238.8 

I40 

122.4 

280 

247-8 

15° 

I3L4 

290 

256.6 

160 

1404 

300 

265.5 

diastatic  value.  The  determination  is  conducted  with  a  normal 
starch  and  a  malt  extract. 

Starch  solution. — To  prepare  this,  a  soluble  starch  is  used.  The 
latter  is  prepared  by  adding  sufficient  7  ^  per  cent,  hydrochloric 
acid  to  cover  any  desired  quantity  of  prime  potato  starch.  This  is 
allowed  to  stand  7  days  at  ordinary  temperature  or  3  days  at  40°. 
The  acid  is  drawn  off  and  the  residue  is  washed  with  cold  water  by 
decantation  until  acidity  ceases.  It  is  then  air  dried.  2  grs.  of 
this  starch  are  dissolved  in  hot  water.  The  solution  will  remain 
clear  for  a  number  of  days,  but  can  be  used  even  after  it  has 
become  turbid. 

Malt  extract. — 25  grs.  kiln-dried  malt  or  crushed  green  malt  are 
extracted  with  500  c.c.  water  at  ordinary  temperature  for  6  hours. 
It  is  then  filtered.  The  solution  is  refiltered  as  long  as  the  filtrate 
comes  through  turbid.  When  green  malt  is  used,  the  filtrate  is 
diluted  with  an  equal  volume  of  water  before  use. 

Experiment. — Introduce  10  c.c.  starch  solution  in  each  of  10  test- 
tubes.  There  is  then  added  to  each  of  these  . i,  .2  —  i  c.c.  malt 
extract.  They  are  well  shaken  and  the  diastase  is  allowed  to  act 
at  the  surrounding  temperature  for  i  hour.  After  this  time  has 
elapsed  5  c.c.  Fehling's  solution  are  added  to  each  of  the  tubes, 
which  are  then  well  shaken  and  placed  for  10  minutes  in  boiling 
water.  The  tube  in  which  all  the  copper  oxide  is  reduced  is  easily 


SPIRITS.  103 

recognized.  In  this  one  the  liquid  over  the  suboxide  appears 
faintly  blue,  whereas  in  the  next  higher  it  is  yellow,  and  in  the  next 
lower  it  is  deep  blue.  In  very  exact  determinations,  another  test  is 
made  between  the  two  limits  found  by  increasing  the  malt  extract 
by  .02  c.c.  and  observing  similar  conditions.  The  fermenting 
value  of  a  malt  is  made  equal  to  100,  according  to  Lintner,  when 
.1  c.c.  of  the  malt  extract,  prepared  as  above,  just  reduces  5  c.c. 
Fehling's  solution.  It  is  graded  in  the  same  proportions  as  the  ex- 
tract used  increases,  /'.  ^.,  .2  c.c.  malt  extract  —  50;  .5  c.c.  malt 
extract  =  20,  etc.  The  fermentation  values  obtained  are  doubled 
when  green  malt,  which  is  diluted  with  an  equal  volume  of  water, 

is  used. 

4.  Yeast. 

Determination  of  fermentation  value. — 50  grs.  yeast,  together 
with  400  c.c.  10  per  cent,  cane  sugar  solution,  are  placed  in  a  flask 
and  closed  with  a  rubber  stopper,  to  which  there  is  attached  a  small 
sulphuric  acid  drying  apparatus.  Flask,  contents  and  drying  appa- 
ratus are  weighed  and  heated  in  a  water-bath  at  exactly  30°  C. 
After  24  hours  the  loss  in  weight,  due  to  the  evolution  of  carbonic 
acid,  is  determined. 

According  to  Heyduck,  compressed  yeast  free  from  starch,  and 
of  which  5  grs.  are  used  for  analysis,  should  yield  8—12  grs.  car- 
bonic acid.  -4904  gr.  carbonic  acid  corresponds  to  i  gr.  cane 

sugar  decomposed. 

5.  Spirits. 

(a)  Alcohol.  When  pure  spirits  are  used,  this  can  be  deter- 
mined by  certain  areometers  and  alcoholometers.  For  this  purpose 
the  officially  adopted  instruments  are  preferably  used.  The  nor- 
mal temperature  is  set  at  12°  R.  in  Austria  and  at  i2|°  R.  in  Ger- 
many. Readings  are  made  at  any  temperature,  and  from  the  ap- 
parent strength  and  the  thermometer  reading  the  true  strength  is 
interpolated  by  means  of  tables  which  accompany  the  instruments. 
The  true  volume  of  the  spirits,  on  the  basis  of  the  true  strength, 
may  be  determined,  by  the  use  of  another  table,  from  the  apparent 
volume,  at  the  prevailing  temperature.  A  third  table  contains  the 
numbers  for  calculation  of  the  weight  of  spirit  into  true  volume. 

When  impure  spirits  are  examined,  such  as  fermented  mashes,  this 
method  is  not  suitable.  The  alcohol  is  in  this  case  determined  by 


104  CHEMICAL-TECHNICAL   ANALYSIS. 

the  method  of  distillation.  For  this  purpose  100-200  c.c.  liquid 
to  be  tested  are  placed  in  a  flask  with  an  equal  volume  of  water 
and  are  distilled  off  exactly  one-half.  The  distillate  contains  all  the 
alcohol  originally  present  in  the  same  quantity  of  liquor  as  before 
distillation.  The  alcohol  may  be  determined  as  heretofore  by  find- 
ing the  density  of  the  distillate  with  an  alcoholometer  or  a  pyk- 
nometer. 

(^)  Fusel  oil.  The  most  convenient  methods  are  that  of  Rose 
and  that  of  Traube  (using  stalagmometer).  The  latter  is  less  re- 
liable, but  can  be  rapidly  executed  and  is  often  sufficiently  exact. 

(a)  Method  of  Rose  (modified  by  Stutzer  and  Reitmair).  This 
depends  on  the  following  principle :  On  shaking  a  mixture  of 
ethyl  alcohol  and  water  with  chloroform,  a  certain  portion  of  the 
former  dissolves  in  the  chloroform,  which  thereby  experiences  an 
increase  in  volume.  When  the  alcohol  contains  fusel  oil  this  is  also 
dissolved.  Therefore  a  greater  increase  of  volume  takes  place. 
The  amount  of  this  latter  increase  affords  a  means  of  establishing 
the  quantity  of  fusel  oil. 

The  agitator  used  consists  of  a  glass  tube,  sealed  at  one  end, 
while  the  other  possesses  a  pear-shaped  enlargement,  provided  with 
a  tightly  fitting  stopper.  The  middle  of  the  tube  is  contracted 
and  graduated.  There  are  two  different  sizes  of  this  apparatus. 
In  the  smaller  form  of  Herzfeld  the  graduation  begins  at  20  c.c. 
and  extends  to  26.  In  the  larger  one  it  begins  at  50  c.c.  and  ex- 
tends to  56.  Both  are  divided  in  .05  c.c. 

Experiment. — The  thoroughly  dry  apparatus  is  suspended  in 
water  of  exactly  15°  C.  and  chloroform  of  15°  C.  is  added  as  far 
as  the  lowest  division  (20  or  50  c.c.).  100  (or  250)  c.c.  of 
the  spirits  under  investigation,  diluted  exactly  to  30  per  cent, 
alcohol  volume,  and  i  c.c.  (or  2.5)  sulphuric  acid  (sp.  gr.  1.286) 
are  added.  The  entire  contents  of  the  burette  are  run  into  the  pear- 
shaped  bulb.  It  is  then  shaken  continuously  and  briskly  about  150 
times,  after  which  it  is  again  suspended  in  water  at  15°  C.  After 
the  chloroform  has  settled  and  the  particles  have  been  removed 
from  the  walls  by  tapping  with  the  finger,  the  chloroform  volume  is 
read  off  on  the  scale.  From  this  the  "  basis"  is  deducted.  The 
* '  basis' '  is  the  increase  in  volume  which  the  chloroform  shows 
when  shaken  with  pure  ethyl  alcohol  free  from  fusel  oil. 


SPIEITS.  105 

Since  this  is  also  dependent  on  the  source  of  the  chloroform 
employed,  it  must  be  determined  anew  when  a  different  chloroform 
is  used.  The  same  sulphuric  acid  must  also  be  used  in  all  deter- 
minations. 

The  requisite  pure  alcohol  is  best  prepared  by  fractional  distilla- 
tion, because  even  the  commercial  product  known  as  "purest"  is 
often  unsatisfactory.  The  remaining  operation  is  conducted  as  be- 
fore. If  now  the  "basis"  be  deducted  from  the  increase  of  vol- 
ume furnished  by  the  spirits  under  investigation,  the  difference  af- 
fords the  increase  due  to  fusel  oil.  From  this  the  per  cent,  volume 
of  fusel  oil  in  the  original  spirits  (not  the  30  per  cent  )  may  be 
found,  when  the  smaller  apparatus  is  used,  by  means  of  the  follow- 
ing formula  : 

d  (ioo-fa) 

150 

where  d  represents  the  difference  between  the  increase  of  vol- 
ume found  and  the  "basis,"  and  a,  the  water  or  alcohol  added 
which  was  necessary  to  dilute  100  c.c.  original  spirits  to  30  per 
cent,  volume.  The  formula  depends  on  observations  made  by 
Stutzer  and  Reitmair,  which  show  that  every  .15  c.c.  increase  in 
volume  corresponds  to  .1  per  cent,  volume  in  the  30  per  cent, 
alcohol.* 

In  using  this  method  the  following  points  should  be  observed  : 
The  spirits  under  examination  must  equal  exactly  30  per  cent,  by 
volume,  /.  e.,  .96564  sp.  gr.  The  most  extreme  limits  allowable  are 
29.95—30.05  per  cent,  volume,  because  only  ±  .1  per  cent,  by 
volume  alcohol  causes  an  increase  in  volume  of  the  chloroform  of 
rfc  .03  c.c.  corresponding  to  .02  per  cent,  by  volume  of  fusel  oil. 
The  quantity  of  water  which  is  necessary  to  dilute  spirits  greater 
than  30  per  cent,  by  volume  to  30  per  cent,  is  found  in  a  set  of 
tables  (also  given  in  the  "  Chemiker  Kalender  "). 

The  temperatuie  must  be  kept  as  near  15°  as  possible  while 
measuring  the  liquid  and  observing  the  volume.  The  utmost  limits 
are  14.5-15.5°.  As  a  correction  for  15°  for  every  .1°  below 
normal  temperature  .01  c.c.  is  added.  Above  normal  this  amount 

*  In  the  larger  apparatus  .15  c.c.  increase  in  volume  represents  .04  per  cent, 
fusel  oil. 


106  CHEMICAL-TECHNICAL    ANALYSIS. 

is  deducted.  When  fine  spirits  are  investigated,  in  which  minute 
quantities  of  fusel  oil  exert  a  great  influence  on  the  value,  Stutzer 
and  Reitmair  recommend  a  concentration  by  fractional  distilla- 
tion when  small  quantities  are  present. 

Since  this  concentration  can  only  be  extended  to  .15  per  cent, 
by  volume,  it  is  necessary  beforehand  to  ascertain  if  this  limit  is 
not  already  overstepped  in  the  original  product.  Should  this  not 
be  the  case,  1000  c.c.  spirits  are  added  to  100  grs.  dry  potash,  or 
if  the  spirits  contain  lower  than  90  per  cent,  by  volume  of  alcohol 
more  potash  is  added.  It  is  placed  in  a  large  distilling  bulb  and 
distilled  from  a  salt-bath  after  2-3  hours.  The  first  500  c.c.  which 
distil  over  are  collected  separately,  as  are  every  subsequent  100  c.c. 
After  all  has  distilled  over,  the  flask  is  allowed  to  cool,  200—250  c.c. 
water  are  added  and  100  c.c.  are  distilled  off.  This  aqueous  dis- 
tillate is  used  to  dilute  the  last  fraction  which  contains  the  entire 
fusel  oil,  providing  that  the  latter  in  the  original  spirits  did  not  ex- 
ceed .  1 5  per  cent.  This  fraction  is  placed  in  the  agitator.  The 
" basis"  determination  can  be  conducted  with  one  of  the  inter- 
mediate fractions  which  is  diluted  to  30  per  cent,  by  volume. 
When  liquids  are  examined  which  contain  substances  having  an 
influence  on  the  volume  increase  (aldehydes,  ether  varieties, 
volatile  acids  and  others  increase ;  ethereal  oils  decrease  the  vol- 
ume), such  as  brandy,  liquors,  etc.,  a  distillation  with  potassium 
hydrate  must  be  carried  out  in  order  to  free  from  these.  For  this 
purpose  200  c.c.  sample  .are  placed  in  a  spacious  distilling  bulb. 
Four-fifths  of  the  volume  is  distilled  off,  the  distillate  is  caught  in  a 
200  c.c.  flask  and  diluted  to  the  mark  with  water  of  15°  temperature. 

(/3)  Traube's  method,  using  the  stalagmometer.  This  depends 
on  the  observation  that  the  size  of  the  drops,  that  is  the  vol- 
ume of  the  drop  which  issues  from  a  capillary  tube  on  a  circular 
smooth  surface,  bears  a  definite  relation  to  the  quantity  of  fusel  oil 
present.  The  apparatus  consists  of  a  bulb  drawn  out  at  both  ends 
to  a  tube.  One  tube,  the  exit  tube,  is  widened  at  the  end  to  a  disk 
which  bears  a  capillary  widened  below  to  a  cone-shaped  opening. 
A  constant  volume  is  confined  between  two  marks  placed  on  the 
tubes.  On  the  instrument  is  etched  the  number  of  drops  which 
this  volume  yields  when  filled  with  a  20  per  cent,  pure  spirit  of  a 
definite  temperature.  The  correction  for  the  above  directions,  at  a 


METHYL    ALCOHOL    (WOOD    SPIRIT).  107 

different  temperature,  is  to  be  found  in  an  explanation  which  ac- 
companies the  apparatus. 

The  spirits  to  be  investigated  are  diluted  to  20  per  cent,  volume. 
The  requisite  quantity  of  water  is  to  be  found  in  the  tables  referred 
to  under  Rose's  method,  after  the  density  has  been  determined 
with  a  pyknometer.  When  ethereal  oils  are  present  in  the  spirits, 
it  must  be  distilled  first  and  the  distillate  then  diluted.  After  the 
liquid  has  arrived  at  the  temperature  of  the  room,  it  is  forced 
into  the  well-cleaned  and  dried  apparatus  by  suction  until  the  upper 
mark  is  reached.  Care  must  be  taken  that  no  air  bubbles  enter.  The 
liquid  is  then  set  at  the  upper  mark  and  allowed  to  run  out  to  the 
lower  mark.  Meanwhile  the  drops  are  counted.  The  last  adhering 
drop  is  taken  into  account.  According  to  Traube,  the  maximum 
error  should  not  exceed  .2  of  a  drop  for  every  100  c.c.  By  this 
operation  .1  to  .05  per  cent,  fusel  oil  can  be  determined.  When 
smaller  quantities,  as  low  as  .02  per  cent.,  are  present,  he  advises 
a  concentration  by  agitation  with  ammonium  sulphate  solution, 
which  dissolves  fusel  oil.  By  distillation  of  this  the  fusel  oil  is 
obtained  in  more  concentrated  form.  The  calculation  is  made 
from  the  difference  between  the  number  of  drops  counted  and 
that  designated  on  the  instrument,  corrected  for  prevailing  tem- 
perature. The  next  lower  difference  on  the  accompanying  tables 
is  found  and  the  fusel  oil  of  the  20  per  cent,  spirit  is  gotten  in  per 
cent,  by  interpolation.  If  the  amount  of  fusel  oil  in  the  tables  = 
b  and  the  water  necessary  to  dilute  100  c.c.  original  substance  to  20 
per  cent,  volume  =  a,  the  fusel  oil  in  per  cent,  by  volume  (f )  in 
the  original  spirits  would  be 

(100+ a)  b 

100 

6.  Methyl  Alcohol  (Wood  Spirit). 

This  finds  use  in  thedyestuff  industry,  as  well  as  for  "denaturiz- 
ing  ' '  spirits  of  wine. 

Impurities  usually  present  in  wood  spirit  are :  Aldehyde,  ace- 
tone, methyl  acetate,  dimethylacetal,  allyl  alcohol  and  ethyl  alco- 
hol. The  quantitative  estimation  of  acetone  alone  will  be  de- 
scribed here. 

The  methods  applied  here  are  based  on  the  fact  that  in  the  pres- 


108  CHEMICAL-TECHNICAL    ANALYSIS. 

ence  of  alkali,  acetone  is  changed  to  iodoform  by  iodine,  whereas 
methyl  alcohol  and  the  other  substances  present  do  not  bring  about 
this  formation.  According  to  the  method  of  Messinger,  which  is 
to  be  described,  a  definite  quantity  of  iodine  is  added  to  form  the 
iodoform,  and  the  excess  of  iodine  is  titrated  back.  1—1.5  c-c- 
wood  spirit  are  placed  in  a  250  c.c.  bottle.  20  c.c.  normal  alkali 
are  added  and  followed  by  20—30  c.c.  -5-  normal  iodine  solution. 
The  whole  is  shaken  briskly  for  ^  minute.  The  alkali  is  now 
exactly  neutralized  with  hydrochloric  acid  (20  c.c,  normal  acid) 
and  the  excess  of  iodine  is  titrated  back  with  a  TV  normal  hypo- 
sulphite solution,  using  starch  paste  as  an  indicator. 

The  number  of  grams  acetone  in  100  c.c.  wood  spirit  (y)  is 
found  by  the  equation  : 

m 
y=n.  7.612, 

where  m  represents  the  quantity  of  iodine  used  in  the  formation  of 
iodoform,  and  n,  the  quantity  of  wood  spirit  used  in  the  analysis, 
expressed  in  c.c. 


VIII.  Fats,  Waxes  and  Mineral  Oils. 


FATS  are  mixtures  of  triglycerides  of  monobasic  fatty  acids. 
Vegetable  and  animal  waxes  are  fatty  acid  esters  of  higher  fatty 
alcohol.  Mineral  waxes  and  mineral  oils  consist  of  hydrocarbons. 

The  groups  named,  representing  different  chemical  constitu- 
tions, show  characteristic  behavior  towards  alkalies.  Fats  are 
saponified  on  treatment  with  alkali  into  salts  of  fatty  acids  (soaps) 
and  glycerin,  both  of  which  are  soluble  in  water.  Fats  are  there- 
fore completely  saponifiable.  Vegetable  and  animal  waxes  yield 
salts  of  fatty  acids  soluble  in  water,  and  insoluble  higher  fatty  alco- 
hols, by  this  treatment,  and  are  termed  incompletely  saponifiable. 
Mineral  waxes  and  oils  are  not  changed  by  alkalies  ;  they  are  unsa- 
ponifiable. 

A.  Fats. 

1.  General  Methods  of  Investigation. 

Although  the  fats  represent  mixtures  of  many  triglycerides,  the 
quantity  of  the  same  in  every  kind  of  fat  is  a  fairly  constant  one. 
In  consequence  of  these  so-called  constants,  slightly  varying  values 
can  be  determined  for  each  fat.  These  would  lead  with  certainty 
to  the  identification  of  the  same.  Of  these  constants  there  will  be 
described : 

(0)  The  saponification  number.  This  indicates  how  many 
milligrams  potassium  hydrate  are  necessary  to  saponify  one  gram  of 
fat,  and  is  therefore  a  representation  of  the  capacity  of  saturation 
of  the  fatty  acid  contained  in  the  fat. 

(3)  Hiibl's  iodine  number.  This  represents  the  quantity  of 
iodine  which  a  fat  is  capable  of  absorbing  and  serves  as  a  measure 
for  the  unsaturated  acids  present  (oleic  acid,  linoleic  and  linolenic 
acid  series). 

(^  The  acetyl  number,  which  is  a  measure  for  the  oxy  fatty 
acids  and  the  fatty  alcohols  present. 


110  CHEMICAL-TECHNICAL   ANALYSIS. 

(</)  The  acid  number,  which  expresses  the  number  of  milligrams 
potassium  hydrate  used  to  neutralize  the  free  fatty  acids  in  a  gram 
of  fat.  It  serves,  therefore,  as  a  measure  for  the  free  fatty  acids 
contained  in  the  fat. 

(#)  Saponification  Number .     {Kottstorfer1  s  Number. ) 

There  are  necessary  to  determine  the  saponification  number  : 

(a)  An  about  ^  normal  hydrochloric  acid,  exactly  standardized 
by  titration  with  potassium  hydrate. 

(/3)  An  alcoholic  potash  solution,  prepared  by  dissolving  in  a 
little  water  30  grs.  caustic  potash,  purified  by  alcohol,  and  then 
diluting  to  i  liter  with  alcohol  free  from  fusel  oil.  After  stand- 
ing one  day  it  is  filtered  into  a  flask.  A  25  c.c.  pipette,  provi- 
ded above  with  a  piece  of  rubber  tubing  and  a  clip,  is  inserted 
into  the  single  perforation  of  a  tightly-fitting  rubber  stopper. 
When  pure  alcohol  is  used  the  solution  will  never  become  brown, 
but  can  at  the  utmost  assume  a  pale  yellow  tint  on  standing  for 
months. 

To  conduct  the  operation  1-2  grs.  are  placed  in  a  wide-necked 
flask  of  150-200  c.c.  capacity.  For  the  purpose  of  weighing,  a 
small  bottle  with  a  lip  is  preferable.  Introduce  50-60  drops  oil 
from  the  weighing-bottle  into  the  flask  and  reweigh  the  bottle. 
25  c.c.  alcoholic  potash  are  now  allowed  to  flow  from  the  pipette 
into  the  flask.  The  drops  which  issue  finally  are  counted,  in  order 
to  observe  equal  conditions,  A  reflux  condenser  is  then  inserted 
through  a  suitable  cork  in  the  flask  and  the  contents  are  heated  to 
boiling  in  a  water-bath  and  agitated  from  time  to  time.  Saponifi- 
cation is  complete  in  15  minutes  as  a  rule,  but  with  difficultly 
saponifiable  fats  ^  hour  is  required.  A  few  drops  of  phenol - 
phthalein  are  added,*  and  the  excess  of  alkali  is  titrated  with  ^ 
normal  hydrochloric  acid. 

Since  the  standard  of  the  alcoholic  potash  alters  somewhat,  25 
c.c.  are  titrated  anew  with  hydrochloric  acid  prior  to  each  experi- 
ment. The  same  conditions  as  heretofore  are  to  be  observed, 
namely,  the  same  period  of  heating  on  the  water-bath,  etc.  The 
difference  between  the  number  of  c.c.  hydrochloric  acid  used  for 

*  It  is  advisable  to  use  alkali  blue  when  the  solutions  are  colored. 


FATS.  Ill 

this  and  the  previous  titration  is  expressed  in  milligrams  K  O  H 
and  calculated  on  i  gr.  fat  to  obtain  the  saponification  number. 

(<£)   v.  HilbV  s  Iodine  Number. 

Whereas  iodine  acts  but  slowly  on  fats,  unsaturated  fatty  acids 
readily  form  chlor-iodine  addition  products  on  treatment  with  an 
alcoholic  solution  of  iodine  and  mercuric  chloride. 

The  materials  necessary  for  this  operation  are  : 

(«)  Iodine  solution.  25  grs.  iodine  and  30  grs.  mercuric  chlor- 
ide are  each  separately  dissolved  in  500  c.c.  95  per  cent,  alcohol 
free  from  fusel  oil.  The  latter  solution  is  filtered  if  necessary. 
They  are  then  united.*  The  liquid  should  stand  24  hours  be- 
fore using,  because  the  standard  rapidly  alters  at  first.  A  2 5  c.c. 
pipette  may  be  inserted,  as  before. 

(/?)  Sodium  hyposulphite  solution.  It  is  made  approximately 
TS  normal.  The  standard  is  best  established  with  a  potassium  bi- 
chromate solution  containing  3,874  grs.  to  the  liter,  10  c.c.  of 
this  solution  equal  .  i  gr,  iodine. 

(y)  Chloroform.  10  c.c.  of  this,  mixed  with  10  c.c.  Hiibl's 
solution,  should  require,  after  2-3  hours,  the  same  amount  of  hypo- 
sulphite as  this  quantity  of  iodine  solution  used  alone. 

(f5)  Potassium  iodide  solution,  i  part  potassium  iodide  to  10 
parts  water. 

(??)  Starch  solution.  Freshly  prepared  i  per  cent,  starch  paste. 
From  .15-.  i8gr.  drying  oils,  -25-.35gr.  non-drying  oils,  or  .8-1  gr. 
solid  fats  is  placed  in  a  500  c.c.  flask,  provided  with  a  tight-fitting 
stopper.  10  c.c.  chloroform  and  25  c.c.  iodine  solution  are  added. 
Should  the  liquid  on  shaking  remain  turbid,  more  chloroform  is 
added.  Should  the  liquid  become  colorless  on  brief  standing, 
another  measured  portion  of  iodine  solution  is  added,  so  that,  in 
fact,  on  standing  6  hours  the  liquid  still  appears  dark  brown.  Sub- 
sequently 20-25  c-c-  potassium  iodide  and  200-300  c.c.  water  are 
added.  Any  red  precipitate  of  mercuric  iodide  which  forms  is  re- 
dissolved  by  addition  of  more  potassium  iodide.  Sufficient  hypo- 
sulphite is  added,  with  frequent  agitation,  to  render  the  aqueous 
liquid  and  the  chloroform  light  in  color.  Starch  paste  is  then 

*  Waller  states  that  Hiibl's  iodine  solution  is  much  more  stable  when  25  c.c. 
hydrochloric  acid  (sp.  gr.  1.19)  are  added  to  500  c.c.  of  the  same. 


112  CHEMICAL-TECHNICAL    ANALYSIS. 

added,  and  the  solution  is  carefully  titrated  to  disappearance  of 
the  blue  color.  A  similar  experiment  is  simultaneously  conducted 
with  25  c.c.  iodine  solution  by  titrating  hyposulphite.  From  the 
difference  the  iodine  absorbed  is  found  and  calculated  into  per  cent. 
Results  are  concordant  when  sufficient  iodine  is  added.  The 
excess  should  about  equal  half  the  iodine  absorbed.  Titration 
should  be  made  after  the  solution  has  stood  6  hours.  Longer  stand- 
ing does  not  in  any  way  influence  the  accuracy  of  the  result. 

(V)  Acetyl  Number. 

The  acetyl  number  of  Ulzer  and  Benedikt  expresses  the  number  of 
milligrams  potassium  hydrate  which  are  necessary  to  saponify  the 
acetyl  groups  in  i  gr.  acetylized  fatty  acids. 

To  determine  this  the  free  fatty  acids  must  first  be  isolated  from 
the  fats,  for  which  purpose  30  grs.  fat  are  placed  in  a  flask  with 
60—70  c.c.  alcohol  and  10  grs.  potassium  hydrate,  dissolved  in  a 
little  water.  This  is  boiled  on  a  water-bath  with  a  reflux  condenser 
to  complete  saponification.  The  latter  is  finished  when,  after  addi- 
tion of  some  water  and  shaking,  the  liquid  remains  perfectly  clear. 
The  excess  of  alcohol  is  evaporated  on  a  water-bath.  The  remain- 
ing soap  is  dissolved  in  warm  water  and  is  poured  into  a  beaker  of 
i  L.  capacity.  The  solution  is  boiled  with  dilute  sulphuric  acid 
until  the  fats  are  completely  melted.  A  current  of  carbonic  acid 
is  meanwhile  run  through  to  prevent  bumping.  Thereupon  the  acid 
fluid  is  siphoned  off  and  the  fats  are  again  boiled  with  water. 
The  acid  liquor  is  again  siphoned,  and  the  operation  is  repeated 
until  the  liquid  siphoned  off  no  longer  reacts  acid.  The  acids  are 
filtered  on  a  hot-water  funnel  through  a  dry  filter,  and  are  acetylized 
by  boiling  2  hours  with  an  equal  volume  acetic  anhydride  in  a  flask 
provided  with  a  reflux.  The  contents  of  the  flask  are  poured  into 
a  beaker  of  about  i  L.  capacity,  are  mixed  with  500-600  c.c.  water, 
and  boiled  for  ^  hour.  As  before,  carbonic  acid  is  conducted 
through  a  capillary  extending  nearly  to  the  bottom.  After  a  time 
the  water  is  siphoned  off  and  the  boiling  with  water  is  repeated 
three  times,  whereby  all  acetic  acid  is  removed.  Finally,  the 
acetylized  acids  are  filtered  in  an  air-bath  at  about  80°  through  a 
dry  filter.  In  a  portion  of  the  acetylized  acids  the  saponification 
number  is  taken  as  in  (a].  This  gives  the  "acetyl  saponification 


FATS. 


113 


number."  In  another  portion  the  "acetyl  acid  number"  is 
determined  in  the  manner  described  below,  in  the  method  for 
acid  number.  The  difference  between  the  two  gives  the  acetyl 
number.  If  a  fat  contain  no  oxy  fatty  acids,  its  acetyl  number 
will  equal  zero. 

(</)  Acid  Number. 

About  10  grs.  fat  are  slightly  heated  in  a  flask  with  about  50  c.c. 
pure  acid-free  95  per  cent,  alcohol  while  the  liquid  is  agitated. 
Upon  cooling,  phenol-phthalein  is  added,  and  the  solution  titrated 
with  y?  normal  alkali  until  the  red  color  appears.  The  number 
of  milligrams  potassium  hydrate  used,  calculated  on  i  gr.  fat, 
yields  the  acid  number.  When  free  fatty  acids  are  used  the  acid 
number  is  identical  with  the  saponification  number.  Frequently 
the  acid  number  of  a  fat  is  expressed  in  Burstyn  degrees.  These 
express  the  number  of  c.c.  normal  alkali  necessary  to  combine  with 
the  free  acids  present  in  100  c.c.  of  the  fat.  The  determination 
of  acid  number  is  also  made  use  of  in  examining  other  fats,  such  as 
those  used  as  lubricants. 

The  following  tables*  contain  the  iodine  numbers  and  saponifica- 
tion numbers  of  the  most  important  fats : 


Fats. 

Iodine  Number. 

Saponification  Number. 

Min. 

Max. 

Mean. 

Min. 

Max. 

Mean. 

Olive  oil  

79 
I03 

87.3 

102 

82 
98 
170 

H0.5 
122 
I23 

Sl 

26 

35-5 
46 

88 

112 

I03 

112 

85-9 
IO4 

I83 
157.5 
134 
166 

52.4 

9-35 
35 
44 
55 

82      83 

I85 
I87 
I90 

I91 
176 

175 
187.4 
I90 
I89 
175 
200 

253 
221 

193 

I96 
I92 

I97 

198 

183 

179 

I95-2 
193 
I94 
194 
202.5 
262 
227 
206 

193 
190 
I94 

195.5 
1  80 
177 
192 

I9I-5 
192 
182—187 
201.5 

257 
224 
197 
190.9 

Sesame  oil 

I  08  —  109 
94—96 

I  08  —  109 

84.5 
100  —  101 

178 

150 
128 

144—148 
51.5 

8-5 
33 
39 
49 

Peanut  oil    (Arachis 
oil)  

Cotton  oil  

Castor  oil  

Rape-seed  oil  

Linseed  oil  

Hemp-seed  oil  

Sunflower-seed  oil...... 
Cod-liver  oil  

Palm  oil  

Cocoanut  oil  

Butter  fat  

Tallow 

Bone  fat 

*  The  maximum  and  minimum  values  expressed  in  the  tables  are  those  found 
only  in  isolated  cases.     Normal  values  are  those  under  the  heading  "  Mean." 

8 


114  CHEMICAL-TECHNICAL    ANALYSIS. 

In  addition  to  the  determinations  mentioned,  the  density  is 
usually  taken.  This  is  done  with  the  liquid  fats  in  a  pyknometer. 
Since,  however,  the  densities  of  one  and  the  same  fat  may  vary 
considerably,  and,  moreover,  since  these  are  approximately  the  same 
for  different  fats,  it  is  only  seldom  that  they  offer  a  reliable  insight. 

Certain  features  will  be  stated,  in  the  chapters  devoted  to  wax, 
mineral  oils  and  soaps,  concerning  determination  and  estimation 
of  unsaponifiable  constituents  of  common  resin  and  colophonium 

rosin. 

2.  Classification  of  FatH. 

This  is  represented  in  the  following  scheme  : 

a.  Liquid  fats. 

a.    Drying  oils. 

ft.   Non-drying  oils. 

y.  Fish  oil. 

rf.  Fluid  waxes. 

b.  Solid  Fats. 

(<z)  Liquid  Fats. 

(a)  Drying  oils.  These  consist  mainly  of  glycerides  of  linoleic 
acid  and  linolenic  acid.  In  thin  layers  they  dry  to  varnish-like 
masses  in  the  air,  thereby  absorbing  much  oxygen,  but  they  do  not 
yield  ela'idin. 

(/?)  Non-drying  oils.  They  contain  much  olein,  and  dry  with 
the  utmost  difficulty  in  the  air  or  at  higher  temperatures.  They 
absorb  little  oxygen  and  give  ela'idin. 

(y)  Fish  oils,  obtained  from  the  fats  of  fish,  absorb  much  oxy- 
gen, do  not  dry  to  a  varnish,  and  yield  little  or  no  ela'idin.  They 
give  intense  colorations  with  caustic  soda,  sulphuric  acid,  nitric 
acid  and  phosphoric  acid,  of  which  that  obtained  with  sulphuric 
acid  serves  to  distinguish  them  from  other  oils.  It  is  obtained  by 
warming  5  vols.  oil  with  i  vol.  glacial  phosphoric  acid.  By  this 
treatment,  all  fish  oils,  whether  mixed  or  not,  give  an  intense  red, 
brown-red  or  brown-black  shade. 

(<5)  Liquid  waxes  from  the  oils  of  marine  animals  consist  mainly 
of  esters  of  monatomic  alcohols,  and  contain  only  a  small  amount 
of  glycerides.*  They  are,  like  true  waxes,  only  partially  saponi- 

*  The  classification  of  these  under  the  fats  is,  therefore,  a  more  or  less  arbitrary 
one. 


CLASSIFICATION    OF    FATS.  115 

fiable,  and  possess,  in  consequence,  a  very  low  saponification 
number.  The  unsaponified  portion  is  solid  and  consists  of  mona- 
tomic  alcohols.  They  contain  only  60-65  Per  cent,  fatty  acids,  as 
against  95  per  cent,  in  other  oils.  They  absorb  little  oxygen  in  air, 
do  not  dry,  and  give  no  elaidin, 

Recognition  of  drying  and  non-drying  oils. — Since  the  thorough 
drying  of  the  oils  in  air,  spread  on  glass  plates  in  thin  layers,  re- 
quires too  long  a  period,  the  determination  can  hardly  furnish  a 
means  of  recognition.  On  the  other  hand,  the  following  methods 
are  suitable  elai'din  tests.  This  depends  on  the  fact  that  glycerides 
of  the  oleic  acid  series  are  transformed  by  nitrous  acid  into  the 
solid  glycerides  of  the  elaidic  acid  series,  whereas  those  of  the 
linoleic  series,  etc.,  remain  liquid. 

10  grs.  oil,  5  grs.  nitric  acid,  40-42°  Be.  and  i  gr.  mercury  are 
placed  in  a  test-tube  and  are  shaken  continuously  for  3  minutes  to 
dissolve  the  mercury.  The  liquid  is  then  allowed  to  stand  for  20 
minutes,  and  is  then  shaken  for  i  minute.  From  this  point  olive 
oil  will,  for  instance,  solidify  in  i  hour,  peanut  oil  in  i  hour  and 
20  minutes,  sesame  oil  in  3  hours  and  5  minutes,  whereas  linseed 
oil  and  fish  oil  give  a  red  pasty  foam  and  hemp- seed  oil  remains 
unaltered. 

Copper  may  be  used  in  place  of  mercury. 

Maiimene* s  test. — This  depends  on  the  phenomenon  that  sul- 
phuric acid,  mixed  with  drying  oils,  heats  up  considerably  more 
than  with  non-drying  oils.  The  test  is  conducted  as  follows  :  50 
c.c.  oil  are  placed  in  a  100  c.c.  beaker.  The  temperature  is  taken 
with  a  thermometer,  and  from  a  pipette  10  c.c.  cone,  sulphuric 
acid  of  the  same  temperature  are  run  in  during  a  period  of  i  min- 
ute, while  the  liquid  is  being  stirred  with  the  thermometer.  To 
prevent  loss  of  heat  the  beaker  containing  the  oil  may  be  placed  in 
a  second  larger  beaker,  with  cotton  placed  between.  It  is  stirred 
until  the  temperature  ceases  to  rise.  Should  the  rise  equal  more 
than  70°,  drying  oils  can  be  considered  present  with  certainty. 
As  examples,*  olive  oil  shows  a  rise  of  41-43°  in  temperature, 
rape -seed  oil  51-60°,  and  linseed  oil  104-111°. 

Iodine    number. — The     non-drying    oils    possess    lower    iodine 

*  According  to  Allen. 


116  CHEMICAL-TECHNICAL   ANALYSIS. 

numbers  than  the  drying  oils.  The  iodine  number,  in  consequence, 
serves  as  a  convenient  and  safe  means  of  identification,  providing 
that  fish  oils  are  absent.  These  are  non-drying,  and  yet  possess  a 
high  iodine  number. 

(£)  Solid  Fats. 

Recognition  of  solid  fats  is  accomplished  chiefly  by : 

(a)  Specific  gravity.  This  is  best  determined  by  the  method  of 
Gintl,  who  uses  a  small  cylindrical,  flat-bottomed  pyknometer,  the 
opening  of  which  may  be  closed  with  a  ground  glass  plate.  When 
filling  in  the  molten  fat  an  excess  is  allowed  to  remain  above  the  top. 
After  cooling,  the  plate  is  slipped  on  and  screwed  down.  The  ex- 
cess is  wiped  off  with  a  cloth  dipped  in  petroleum  ether.  The 
weights  of  empty  and  filled  flasks  are  determined  in  the  usual 
manner. 

According  to  the  method  of  Hager  for  the  determination  of 
specific  gravity,  the  molten  fat  is  allowed  to  drop  a  short  distance 
into  a  glass  dish  filled  with  60—90  per  cent  alcohol.  The  solidified 
drops  are  placed'  in  the  liquids  which  serve  to  determine  specific 
gravity.  For  densities  less  than  water  a  mixture  of  water  and  alco- 
hol, and  for  greater  densities  a  mixture  of  glycerin  and  water  or 
alcohol,  or  alcohol  and  water  respectively.  Glycerin  or  glycerin 
and  water  are  added  until  the  drop  just  floats  on  the  liquid,  which  is 
set  in  rotation.  Finally  the  liquid  is  poured  through  glass  wool, 
and  the  specific  gravity,  which  is  equal  to  that  of  the  fat,  is  then  de- 
termined with  areometer  or  pyknometer.  The  determination  of 
ithe  specific  gravity  of  molten  fats  may  be  conducted  with  the 
Westphal  balance.  The  vessel  containing  the  fat  is  placed  in  a 
paraffin  bath. 

(/3)  The  melting  point  and  solidification  point  of  a  fat  and  of 
isolated  fatty  acids.  Fuller  directions  will  be  given  in  the  discus- 
sion of  tallow  and  wax. 

(f)  The  behavior  in  the  refractometer.  The  latter  is  used 
chiefly  in  testing  butter,  fat  and  lard.  For  apparatus  and  descrip- 
tion see  Benedikt  and  Ulzer,  Analyse  der  Fette  und  Wachsarten, 
3.  Aufl. 

(rf)  Saponification  and  iodine  numbers.  The  saponification  and 
iodine  numbers  of  the  most  important  fats  are  given  in  the  tables, 
p.  113. 


EXAMINATION    OF   A   FEW    COMMON   FATS.  117 

0?)  Volatile  fatty  acids.  These  are  determined  by  the  Reichert- 
Meissl  number,  which  represents  the  number  of  c.c.  TV  normal 
alkali  which  are  necessary  to  neutralize  the  volatile  fatty  acids  in 
5  grs.  fat. 

About  5  grs.  fat  are  placed  in  a  200—300  c.c.  flask  on  a  water- 
bath  with  about  2  grs.  stick  potash  and  50  c.c.  of  70  per  cent, 
alcohol  and  saponified.*  The  flask  and  contents  are  shaken  from 
time  to  time. 

The  alcohol  is  volatilized  after  complete  saponification  until  a 
thick  soap  remains.  This  is  dissolved  by  warming  with  100  c.c. 
water.  40  c.c.  sulphuric  acid  (i  :  10)  and  a  few  pieces  of  pumice- 
stone  are  added  to  the  flask,  which  is  then  connected  with  a  Liebig 
condenser  by  means  of  a  bulb  tube.  It  is  first  heated  with  a  small 
flame  until  the  fats  have  melted  to  a  clear  layer,  after  which  it  is 
distilled  for  a  half  hour  and  exactly  no  c.c.  distillate  are  collected 
in  a  graduated  flask.  After  shaking,  100  c.c.  are  filtered  off  in  a 
measuring  flask,  emptied  into  a  beaker  and  titrated  with  iV  normal 
alkali,  using  phenol-phthalein  as  indicator.  The  quantity  of  the 
alkali  used  is  increased  TV  and  calculated  on  5  grs.  fat. 

The  Reichert-Meissl  number  is  principally  used  to  identify  butter 
and  cocoanut  oils.  Butter  has  a  number  between  26-29;  cocoa- 
nut  oil,  7. 

3.  Examination  of  a  Few  Common  Fats. 

O)   Olive  Oil. 

The  iodine  number  and  saponification  numbers  are  taken.  Should 
these  correspond  to  the  mean  values  given  in  the  table,  the  oil  may 
be  considered  pure.  Should  the  saponification  number  correspond, 
but  the  iodine  number  lie  above  85,  adulteration  with  sesame  oil, 
peanut  oil,  or  cotton-seed  oil  has  been  attempted.  The  methods, 
specially  described,  may  be  used  for  detecting  their  presence. 

Should  the  saponification  number  be  low  and  the  iodine  number 
high,  the  adulterant  is  presumably  rape-seed  oil.  In  this  case  a 
test  for  mineral  oil  must  also  be  made.  When  used  for  machine 
oil  the  acid  number  should  not  exceed  16. 

*  Kreiss  and  some  others  recommend  the  use  of  sulphuric  acid  instead  of 
potash. 


118  CHEMICAL-TECHNICAL    ANALYSIS. 

(£)  Rape-seed  Oil. 

The  normal  values  for  iodine  and  saponification  numbers,  as  a 
rule,  suffice  for  identification.  Drying  oils  and  fish  oil  raise  the 
iodine  and  saponification  numbers.  Rosin  oil  and  mineral  oil 
lower  the  same.  When  used  for  lubricating  purposes  the  acid 
number  should  not  exceed  6. 

(c}   Castor  Oil. 

Iodine  number  and  saponification  number,  acetyl  number  and 
density,  serve  to  determine  the  purity.  The  acetyl  number 
should  not  exceed  15.2;  the  density,  .960— .966.  Castor  oil  must 
completely  dissolve  in  two  parts  by  volume  of  95  per  cent,  alcohol, 
and  remain  insoluble  in  petroleum  ether. 

(</)  Sesame  Oil. 

This  is  frequently  adulterated  with  cotton-seed  oil.  Iodine  num- 
ber, saponification  number  and  density  do  not  afford  sufficient  means 
for  identification.  The  Livache  test  is  particularly  suited  to  this 
purpose.  It  depends  on  the  fact  that  the  increase  in  weight  due  to 
oxygen  absorption  is  perceptibly  less  in  the  presence  of  cotton -seed 
oil  than  in  the  genuine  article.* 

The  test  of  Livache  is  conducted  by  precipitating  the  solution  of  a 
lead  salt  with  zinc.  The  precipitate  is  quickly  washed  with  water, 
alcohol  and  ether,  and  dried  in  a  vacuum  over  sulphuric.  Two 
quantities  of  lead  powder,  each  i  gr. ,  are  spread  out  on  two  large 
watch  crystals.  The  weight  of  each  lead  powder  and  crystal  are 
taken  and  20  drops  of  oil  placed  on  one  of  the  watch  crystals  from 
a  finely-drawn-out  pipette.  On  the  other  is  placed  the  same  quan- 
tity of  the  fatty  acids  of  the  same  in  such  a  manner  that  the  drops 
do  not  flow  together.  Both  watch  crystals  are  again  weighed  in 
order  to  obtain  the  weight  of  oil  and  fatty  acids  and  are  set  in 
a  place  protected  from  dust.  They  are  allowed  to  remain  in  the 
light  on  the  average  seven  days  at  ordinary  temperature.  When 
this  time  has  elapsed,  the  increase  in  weight  of  each  is  determined 
and  reckoned  in  percentage  of  substance  taken.  Presence  of  cot- 
ton-seed oil  is  detected  by  this  means. 

*  The  increase  in  weight  of  the  oils  and  fatty  acids  of  oils,  such  as  sesame 
and  most  of  the  others,  in  the  same  time,  is  of  nearly  equal  percentage. 


EXAMINATION    OF    A    FEW    COMMON    FATS.  119 

Detection  of  sesame  oil  mother  oils. — According  to  Baudouin,  20 
c.c.  oil  under  investigation  are  placed  in  a  test-tube  containing  .1 
gr.  cane  sugar  and  10  c.c.  hydrochloric  acid  (sp.  gr.  1.19).  It  is 
well  shaken  for  a  minute  and  allowed  to  settle.  The  layer  of 
liquid,  which  separates  immediately,  as  a  rule,  shows  an  intense  red 
color  in  the  presence  of  sesame  oil,  whereas,  in  absence  of  same, 
the  aqueous  layer  remains  colorless  at  least  2  minutes  and  the  oily 
layer  appears  green  or  yellow. 

Villavecchia  and  Fabris  attribute  the  red  coloration  to  the  fur- 
furol  formed  from  the  laevulose,  which  is  formed  by  the  action  of 
hydrochloric  acid  on  cane  sugar,  and  demonstrate  this  by  showing 
that  a  2  per  cent,  alcoholic  solution  of  furfurol  gives  the  same  re- 
action. They  therefore  propose  the  use  of  this  reagent  in  place  of 
cane  sugar. 

(<?)  Arachis   Oil.      {Peanut  Oil.) 

This  is  characterized  by  the  iodine  number  and  saponification 
number  given  in  the  tables  as  well  as  the  rise  of  temperature,  which 
equals  45.5-51.4°  with  Maumene's  test.  Additions  of  peanut  oil 
to  other  oils  can  be  detected,  according  to  De  Negri  and  Fabris, 
by  the  fact  that  the  soap  solutions  obtained  in  the  saponification 
number  solidify  comparatively  easy.  An  olive  oil  diluted  with 
10  per  cent,  peanut  oil  after  determination  of  the  saponification 
number  gives  a  turbid  liquid  which  subsequently  deposits  a  pre- 
cipitate of  the  potassium  salt  of  arachidic  acid. 

The  presence  of  arachidic  acid,  which  melts  as  high  as  75°,  in 
peanut  oil  can  be  serviceable  in  detecting  the  latter  when  present 
in  other  oils.  The  procedure  of  Renard,  modified  by  De  Negri 
and  Fabris,  is  conducted  as  follows  : 

10  grs.  sample  are  saponified.  The  fatty  acids  are  separated 
with  hydrochloric  acid,  dissolved  in  50  c.c.  90  per  cent,  alcohol, 
and  precipitated  in  the  cold  with  a  solution  of  lead  acetate.  It 
is  decanted  after  standing  12  hours.  The  residue  is  digested  with 
ether  to  separate  lead  oleate,  and  the  precipitate,  consisting  of  lead 
palmitate  and  lead  arachitate,  is  separated  from  the  liquid  by  decan- 
tation.  It  is  finally  filtered,  and  the  precipitate  is  washed  with  ether 
until  the  filtrate  no  longer  shows  a  residue  on  evaporation.  The 
lead  salts  are  decomposed  in  a  separatory  funnel  with  hydrochloric 
acid  (i  :  5).  Ether  is  added,  the  liquid  is  agitated,  and  when  the 


120  CHEMICAL-TECHNICAL    ANALYSIS. 

two  layers  have  separated  the  aqueous  portion  is  run  off.  The 
ethereal  layer  is  then  withdrawn,  the  ether  is  distilled  off,  and  the 
residue,  consisting  of  fatty  acids,  is  dissolved  in  50  c.c.  hot,  90  per 
cent,  alcohol.  Upon  cooling,  a  copious  crystalline  precipitate  of 
arachidic  acid  separates.  It  is  filtered  and  washed  at  first  with  90 
per  cent,  alcohol,  and  later  with  70  per  cent,  alcohol,  is  weighed, 
and  the  melting  point  is  taken.  The  latter  usually  is  70—71°,  be- 
cause the  acid  is  not  quite  pure. 

(/)   Tallow. 

In  addition  to  the  constants,  the  determination  of  the  freezing 
point  of  the  fatty  acids,  the  so-called  "  titer  test"  is  of  especial 
importance.  In  order  to  obtain  concordant  results,  the  following 
method  was  proposed  by  Wolf  bauer  : 

25  c.c.  potassium  hydrate,  sp.  gr.  1.509  (125  grs.  stick  potash  in 
100  c.c.  water),  are  stirred  with  120  grs.  molten  sample  in  a  beaker. 
The  temperature  should  be  only  slightly  above  the  melting  point  of 
the  tallow.  It  is  placed  in  a  compartment  at  100°  after  being  agita- 
ted, mixed,  and  covered  with  a  watch  glass.  It  is  permitted  to  remain 
there,  with  occasional  stirring,  until  the  saponification  is  complete, 
and  a  drop,  warmed  with  50  per  cent,  alcohol,  completely  dis- 
solves, which  is  the  case  after  about  2  hours.  150  c.c.  boiling 
Water  are  stirred  into  the  soap,  which  is  then  poured  into  a  dish, 
treated  with  165  c.c.  sulphuric  acid,  sp.  gr.  1.143  (22  c-c-  cone, 
sulphuric  acid  and  150  c.c.  water),  and  boiled  until  the  fatty  acids 
form  a  perfectly  clear  layer. 

The  acid  liquid  is  withdrawn  entirely  with  a  siphon  and  the  fatty 
acids  are  boiled  with  weak  sulphuric  acid  (5  c.c.  cone,  sulphuric 
acid  in  100  c.c  water),  which  is  then  again  withdrawn,  after  which 
they  are  twice  boiled  out  with  100  c.c.  water.  The  fatty  acids  are 
eventually  dried  for  2  hours  at  100°.  The  solidified  acids  are 
melted  in  a  water-bath  and  filled  to  within  i  ^  cm.  into  a  thin  wall 
test-tube  of  15  cm.  length  and  3.5  cm.  diameter.  The  test-tube 
is  then  suspended  in  a  specimen  bottle  by  means  of  a  cork.  There- 
upon a  thermometer,  graduated  in  one-fifth  degree  as  far  as  60°,  is 
inserted  through  a  cork  into  the  fatty  acids  in  such  a  manner  that 
while  four-fifths  cm.  distant  from  the  bottom  it  is  submerged  to  35th 
division. 


WAXES. 


121 


The  clear  mass  is  stirred  with  the  thermometer  until  no  longer 
transparent,  and  until  the  thermometer-reading  on  repeated  stirring 
no  longer  changes.  The  thermometer  is  then  fastened.  The 
mercury  begins  to  rise,  due  to  liberation  of  latent  heat  of  fusion. 
The  highest  mark  which  it  touches,  and  at  which  it  becomes  station- 
ary, is  read  off  and  taken  as  the  freezing  point.  The  difference  be- 
tween two  determinations  should  not  exceed  .1°.  Frequently  the 
iodine  number  of  the  fatty  acids  of  tallow  is  taken.  The  number 
multiplied  by  1.1102  gives  the  oleic  acid  in  the  fatty  acids.  When 
used  for  lubricating  purposes,  tallow  should  not  contain  more  than 
.5  per  cent  matter  insoluble  in  chloroform. 

B.  Waxes. 

As  has  been  mentioned,  waxes  are  of  animal  and  vegetable  origin. 
They  are  partly  saponifiable  and  separate  insoluble  higher  fatty 
alcohols.  Mineral  waxes  are  unsaponifiable.  The  saponification 
number  affords  a  sure  basis  of  distinction. 

1.  Vegetable  and  Animal  Waxes. 

Following  determinations  are  chiefly  resorted  to  in  examining 
vegetable  and  animal  fats  :  Acid  number,  saponification  number, 
ester  number  (the  difference  between  saponi- 
fication and  acid  numbers),  specific  gravity, 
melting  point  and  freezing  point.  These  de- 
terminations are  generally  conducted  accord- 
ing to  the  methods  previously  mentioned. 

The  specific  gravity  can  be  determined,  in 
addition  to  the  methods  already  given,  with 
the  Sprengel  tube.  This  is  a  U  tube  (Fig.  10) 
of  about  1 8  c.c.  capacity  and  n  mm.  exter- 
nal diameter,  which  tapers  at  both  ends  to 
narrow  bent  tubes  a  and  ^,  of  which  the  one 
is  longer  and  is  provided  with  a  mark,  m. 
The  molten  fat  or  wax  is  brought  into  the 
tube  by  suction,  during  which  operation  the 
longer  bent  tube  is  dipped  in  the  fat.  It  is 
now  brought  into  a  water-bath  of  constant 

. ,     i  j  FIG.  10. — Sprengel  Tube. 

temperature  until  the  wax  ceases  to  expand, 

and  the  excess  in  the  shorter  arm  is  removed  with  filter  paper 


122  CHEMICAL-TECHNICAL    ANALYSTS. 

until  the  longer  arm  is  just  filled  to  the  mark.  It  is  allowed  to 
cool,  and  the  tube  is  cleaned  and  weighed.  The  experiment  is 
repeated  with  water  at  the  same  temperature  or  at  15°.  The  melt- 
ing point,  according  to  Pohl,  is  usually  determined  by  finding  the 
temperature  when  the  wax  fuses.  To  this  end  the  bulb  of  a  ther- 
mometer is  dipped  for  a  moment  in  the  fat  or  wax,  which  is  heated 
slightly  above  its  melting  point  so  that  a  film  will  remain  on  re- 
moving. The  thermometer  is  allowed  to  stand  a  while  and  is  then 
inserted  through  a  cork  into  a  long,  wide  test-tube  so  that  the  bulb 
rests  i  cm.  from  the  bottom.  The  test-tube  is  held  with  a  test-tube 
holder  2-3  c.c.  over  a  tin  shield  or  an  asbestos  plate  which  is  care- 
fully heated  with  a  burner.  The  point  is  noticed  at  which  the  wax 
becomes  transparent  when  a  drop  of  molten  wax  will  appear  at  the 
lower  end. 

Frequently  the  molten  fat  is  drawn  into  a  thin  walled,  not  too 
narrow,  capillary  tube,  so  that  a  column  of  1—2  cm.  is  formed.  The 
end  is  then  sealed,  and  the  tube  is  fastened  on  a  thermometer  so 
that  the  column  of  fat  is  on  a  level  with  the  mercury  bulb. 

As  soon  as  the  substance  has  solidified — better  after  24  hours — 
the  thermometer  is  placed  in  a  3  cm.  wide  test-tube  containing  the 
heat  conductor  (glycerin).  The  temperature  is  taken  the  moment 
the  fat  flows  to  a  clear  liquid. 

Examination  of  Beeswax  for  Adulterants. 

(0)  Determination  of  total  acid  number.  In  consequence  of 
the  difficulty  experienced  in  the  saponification  of  many  waxes  with 
alcoholic  potash,  especially  when  they  contain  paraffin  or  ceresin, 
too  low  results  are  often  obtained.  Benedikt  and  Mangold  there- 
fore determine  the  total  acid  number  instead  of  the  saponification 
number,  that  is,  the  number  of  milligrams  caustic  potash  required 
to  neutralize  i  gr.  of  the  mixture  of  fatty  acids  and  alcohol  which 
is  set  free  from  the  wax  by  saponification  of  the  wax  and  subsequent 
decomposition  of  the  soap  obtained  by  boiling  with  dilute  hydro- 
chloric acid.  The  mixture  is  termed  "decomposed  wax."  In 
order  to  prepare  the  latter  20  grs.  potassium  hydrate  are  dissolved 
in  15  c.c.  water  in  a  hemispherical  capsule  of  350—500  c.c.  capac- 
ity. The  solution  is  heated  to  boiling,  when  about  20  grs.  pre- 
viously-melted wax  are  stirred  in.  The  solution  is  heated  10  min- 


WAXES.  123 

utes,  with  constant,  brisk  stirring,  over  a  small  flame.  200  c.c. 
water  are  added,  the  mass  is  heated  and  acidified  with  40  c.c. 
hydrochloric  acid,  previously  diluted  with  a  little  water.  There- 
upon it  is  boiled  until  the  upper  layer  becomes  perfectly  clear.  It 
is  allowed  to  cool  and  is  boiled  out  three  times  with  portions  of 
water,  to  the  first  of  which  hydrochloric  acid  has  been  added.  The 
cake  is  finally  removed,  wiped  off  with  filter  paper,  is  melted  in  a 
drying  oven  and  filtered.  The  filtered  fat  is  poured,  still  liquid, 
on  a  watch  crystal,  and  is  broken  up  after  cooling.  For  the  esti- 
mation of  total  acid  number  6—8  grs.  of  the  decomposed  wax  so 
obtained  are  covered  with  alcohol  free  from  acid,  are  heated  on  a 
water-bath,  and  titrated  after  addition  of  phenol-phthalein.  Even 
when  a  large  amount  of  ceresin  is  present,  the  saponification  is 
usually  complete.  The  total  acid  number  lies  somewhat  lower  than 
the  saponification  number,  about  92.8  on  an  average,  according  to 
v.  Hiibl. 

(ft)  Determination  of  ceresin  and  paraffin. 

The  quantity  of  paraffin  or  ceresin  present  may  approximately  be 
ascertained  on  the  basis  of  the  total  acid  number  S  by  means  of  the 
following  formula  : 

100  S 

P=IOO-^1T' 

where  P  =  paraffin  or  ceresin  and  92.8  the  average  total  acid 
number  of  pure  beeswax. 

The  test  of  A.  u.  P.  Buisine  is  useful  in  the  exact  determination 
of  the  paraffin  or  ceresin.  This  depends  on  the  fact  that  the  fatty 
alcohols,  on  heating  with  soda-lime,  disengage  hydrogen  with  for- 
mation of  the  sodium  salts  of  corresponding  fatty  acids  according 
to  the  equation  : 

C15H31  CH.2OH  -f  NaOH  =  C1BH81COO  Na  +  2  H2 
Cetyl  alcohol.  Sodium  palmitate. 

A  subsequent  extraction  with  ether  or  petroleum  ether  removes, 
beside  paraffin  and  ceresin,  only  the  hydrocarbons  of  the  wax.* 

To  accomplish  this,  2-10  grs.  sample  are  melted  in  a  small  porce- 
lain crucible,  and  to  it  is  added  an  equal  volume  of  powdered 
caustic  potash.  It  is  stirred,  and  on  cooling  a  hard  mass  is  obtained 

*  The  quantity  of  hydrocarbons  in  beeswax  varies  between  12-14.5  per  cent. 


124  CHEMICAL-TECHNICAL   ANALYSIS. 

which  is  pulverized  and  uniformly  mixed  with  3  parts  soda-lime 
(for  i  part  wax). 

The  mixture  is  now  heated  in  a  small  flask  or  a  test-tube,  at  250°, 
for  2  hours.  The  powdered  residue,  if  necessary,  together  with 
the  adhering  broken  glass,  is  powdered  and  extracted  in  a  flask  or 
extractor  with  ether  or  petroleum  ether.  The  liquid  is  filtered,  if 
required,  the  solvent  is  distilled  off,  and  the  last  adhering  traces  are 
vaporized  in  a  current  of  air.  The  residue  is  weighed.  If  p  — 
the  percentage  of  hydrocarbons  found,  C  the  ceresin  or  paraffin, 
then,  according  to  Mangold,  if  the  hydrocarbons  in  genuine  wax 
be  taken  at  13.5  per  cent.  : 

_  IPO  p— 1350 
86.5 

(c}  Determination  of  stearic  acid.  Stearic  acid  heated  with 
alcohol  dissolves,  together  with  ceresin,  but,  unlike  the  latter,  it 
does  not  separate  so  readily  on  cooling. 

Therefore,  if  i  gr.  wax  be  boiled  for  several  minutes  with  10  c.c. 
80  percent,  alcohol  in  a  test-tube  18-20  mm.  wide,  and  allowed  to 
cool  to  18—20°,  then,  upon  adding  water  to  the  solution,  filtered 
into  a  similar  test-tube,  the  liquid  becomes  slightly  turbid  if  it  con- 
tain pure  wax,  whereas,  when  stearic  acid  is  present,  a  flocculent 
precipitate  is  formed.  Even  with  only  i  per  cent,  stearic  acid  a 
perceptible  precipitate  is  formed.  On  the  strength  of  the  acid 
number,  the  stearic  acid  may  be  approximately  calculated.  The 
acid  numbers  of  pure  beeswax  and  stearic  acid  are  respectively  20 
and  195.  Let  that  of  the  sample  =  S.  Then  the  stearic  acid 

K__  IPO  (S— 20)  ^ 

175 

The  absence  of  other  acids,  including  those  of  rosin,  is  taken  for 
granted. 

(dQ  Determination  of  neutral  fat. 

Since  pure  wax  yields  no  glycerin,  but  fats  contain  an  average  of 
10  per  cent.,  the  neutral  fat  may  be  approximately  determined  on 
the  strength  of  the  amount  of  glycerin  present,  by  multiplying  the 
latter,  which  is  found  by  the  permanganate  method  (see  Glycerin, 
p.  141)  by  10. 

e~    Determination  of  carnauba  wax. 


MINERAL    OILS. 


125 


When  present,  this  wax  decreases  the  acid  number,  while  the 
ether  number  remains  unchanged.  Specific  gravity  and  melting 
point  are  increased. 

(/)  Determination  of  rosin.  The  most  applicable  qualitative 
test  for  rosin  is  the  reaction  of  Morawski  and  Storch  (see  Mineral 
Oils,  p.  129).  The  methods  of  Twitchell  or  Gladding  (see 
Soaps,  p.  137)  may  be  used  for  quantitative  purposes,  but  in  this 
case  myricyl  alcohol  and  other  unsaponified  matter  must  previously 
be  removed  from  the  saponified  sample. 

2*  Mineral  Waxes. 

Melting  point,  freezing  point  and  specific  gravity  are  the  tests 
applied  to  mineral  wax.  The  methods  employed  by  buyer  and 
seller  should  be  identical,  because  the  results  obtained  by  different 
methods  differ  not  inconsiderably.  The  insolubility  of  ceresin  and 
paraffin  in  boiling  acetic  anhydride  distinguishes  these  from  the 
fatty  alcohols.  The  latter  remain  entirely  dissolved  in  the  heat  and 
partially  in  the  cold. 

The  loss  of  weight  of  ozokerite  (earth  wax)  on  heating  at  150° 
is  also  determined.  It  should  not  exceed  5  percent.  The  earthy 
constituents  are  determined  by  dissolving  in  benzine  and  weighing 
the  residue. 

The  following  table  contains  the  most  important  data  of  the 
most  common  waxes : 


Wax. 

Specific 
Gravity  at 
i5°. 

Melting 
Point. 

Freezing 
Point. 

Acid 
Number. 

SaponiSca- 
tion. 

Iodine 
Number. 

Carnauba  wax  

0.990—0.999 

83°-85° 
620-650 
81  —  83° 

44°        A.  7° 

8o°—  81° 
60.5°—  62° 
80.5°—  81° 
43.40-44.2° 

y. 

4-8 
18.6—21 

0—5-17 

80—95 
91—97 

63—77.9 
125.8  —  134.6 

13.5 
8—  n 

Chinese  wax  

0.926  —  0.970 
0.942  —  0.960 
vai 
0.918  —  0.922 

Paraffin 

y  considerab 
61°  —  78° 

'Ceresin  

C.  Mineral  Oils. 

Mineral  oils  are  either  distillation  products  of  bituminous  coal  or 
bituminous  shales,  etc.,  or  else  their  origin  is  crude  petroleum, 
from  which  they  are  likewise  gotten  by  distillation.  Their  use  is 
mainly  for  lubricating  and  illuminating  purposes.  The  higher  dis- 


126  CHEMICAL-TECHNICAL    ANALYSIS. 

tillation  products  of  petroleum  or  shale,  termed  ' '  heavy  oils, ' ' 
are  used  as  lubricants;  while  the  lower  boiling  fractions  of  shale 
oil  are  used  for  illuminating  purposes  under  the  names  solar  oil, 
illuminating  oil,  and  those  from  crude  petroleum  as  petroleum. 

The  gas  oils,  likewise  from  shale  oil,  are  used  mainly  in  oil  gas 
factories,  while  the  lowest  distillation  products  (light  shale  oil,  pho- 
togen  on  the  one  hand ;  gasoline,  naphtha,  benzine  on  the  other) 
are  used  as  solvents  for  fats,  etc. 

1.  Mineral  Lubricants. 

The  viscosity,  specific  gravity,  flash  point,  burning  point,  acidity, 
rosin,  fatty  oils,  rosin  oils,  and,  if  necessary,  coal-tar  oils,  are  the 
tests  usually  undertaken. 

(#)  Viscosity.  The  viscosity  or  body  of  an  oil  is  measured  by 
comparing  the  time  it  takes  for  a  given  quantity  of  oil  to  flow  from 
a  narrow  opening,  with  the  time  it  takes  an  equal  amount  of  water 
to  flow  out.  The  latter  is  taken  as  i. 

The  most  convenient  of  the  viscosimeters  is  that  of  C.  Engler 
(Fig.  n).  The  vessel  containing  the  oil  under  investigation  con- 
sists of  a  smooth  box  (A)  of  brass,  provided  with  a  lid  (A'}.  The 
form  and  dimensions  are  indicated  in  the  figure.  Connected  with 
the  conical  bottom  is  a  20  mm.  long  tube  (a)  which  is  almost  ex- 
actly 3  mm.  in  width.  It  is  usually  made  of  brass.  It  may  be 
opened  and  closed  by  means  of  a  plug  (<£). 

Four  level-marks  (V)  serve  to  measure  off  the  oil  sample  and  to 
give  means  for  keeping  the  level  in  the  box  horizontal.  Filled  to 
the  mark,  the  apparatus  should  hold  240  c.c.  The  box  (A}  is  sur- 
rounded by  a  jacket  (BB)  made  of  brass,  and  is  open  at  the  top. 
This  serves  to  hold  suitable  fluid,  by  which  the  contents  of  A  can 
be  brought  to  the  desired  temperature. 

The  thermometers  /  and  t'  record  the  temperature  of  the  oil  to  be 
tested  and  the  liquid  in  the  jacket.  The  apparatus  rests  on  a  tripod. 
The  measuring  flask  C,  under  the  exit-tube,  is  provided  in  its  neck 
with  the  marks  200  and  240.  The  neck  is  enlarged,  in  order  to 
shorten  the  escaping  column. 

Regulation  of  the  apparatus. — 240  c.c.  water  are  placed  in  the 
box,  which  is  previously  cleaned  with  ether,  alcohol  and  water,  and 
plugged.  The  temperature  is  brought  to  20°.  To  do  this  the 


MINERAL    LUBRICANTS. 


127 


water  contained  in  the  jacket  {BB}  is  maintained  at  this  tempera- 
ture until  the  inner  thermometer  registers  exactly  20°.  In  the  mean- 
while the  flask  is  allowed  to  drain.  It  is  then  placed  under  the 
vent  and  the  plug  is  withdrawn.  The  time  is  recorded  in  seconds, 
by  a  second-watch  or  chronometer,  which  elapses  while  the  flask  is 
filled  to  200.  Before  allowing  the  oil  to  run  out,  it  must  have  come 
to  complete  repose.  The  time  required  to  issue  should  lie  between 


FIG.  ii. — Viscosimeter  of  Engler. 

50  and  55  seconds  when  the  apparatus  is  properly  constructed. 
The  mean  is  taken  of  three  determinations,  which  should  not  differ 
by  more  than  %  minute.  This  time  is  taken  as  i. 

Oil  test. — In  the  next  operation  all  moisture  is  removed  from  the 
box  by  drying  and  rinsing  with  alcohol,  then  with  ether.  The  ap- 
paratus is  filled  to  the  mark  with  the  oil  in  question.  Only  thin 
oils  can  be  filled  in  with  a  measuring  flask.  It  is  then  brought  to 


128  CHEMICAL-TECHNICAL  ANALYSIS. 

the  desired  temperature  by  heating  the  jacket  (BB~},  which  con- 
tains water  or  oil.  The  temperature  must  remain  constant  at  least 
3  minutes  before  the  operation  is  begun.  Determination  of  the 
time  of  issue  is  then  conducted  as  before. 

The  lowest  grade  for  an  oil  which  is  to  be  used  as  a  lubricant  is, 
according  to  Engler,  a  degree  of  viscosity  of  2.6  at  20°,  water  rrr 
i.  With  viscosity  determination  of  lubricants  the  rule  holds  good 
that  the  temperature  used  should  lie  near  that  which  the  oil  will 
assume  while  in  use  (machine  oil  50°,  cylinder  oil  150°). 

In  order  to  maintain  an  even  temperature  above  50°  for  a  longer 
period,  the  later  forms  of  apparatus  are  provided  with  a  ring  burner 
the  gas  flames  of  which  heat  the  liquid  in  the  jacket.  In  addition, 
the  rod  of  the  plug  issues  from  an  opening  in  the  lid,  so  that  it  can 
be  withdrawn  without  removing  the  lid.  The  liquid  for  the 
jacket  and  the  oil,  in  this  case  as  well  as  with  the  older  forms 
of  apparatus,  should  be  heated  to  the  required  point  and  poured  in. 

Fatty  oils  as  well  as  lubricants  are  subjected  to  the  viscosimetric 
test.  In  many  cases,  such  as  rape-seed  oil,  the  viscosity  is  so  large 
and  so  constant  that  it  can  serve  as  a  test  for  purity. 

(b)  Specific  gravity  is  determined  with  an  areometer  or  a  pyk- 
nometer. 

(V)  Flash  and  burning  points.  A  crucible  6  cm.  upper  diameter 
and  6  cm.  high  is  filled  with  oil  to  within  i  cm.  of  the  rim. 

The  mercury  bulb  of  a  thermometer  is  then  immersed  with  the 
end  i  cm.  above  the  bottom,  which  is  best  accomplished  by  first 
resting  the  thermometer  on  the  bottom  and  subsequently  raising  the 
same  i  cm.  The  crucible  is  warmed  in  a  sand-bath,  and  when  the 
temperature  has  overstepped  120°  a  small  flame,  preferably  a  pea- 
sized  flame  of  a  burner,  is  passed  over  the  surface  of  the  oil  at  the 
same  height  as  the  crucible  rim  at  every  increase  of  5°.  As  soon 
as  the  first  faint  explosion  of  oil -vapor  saturated  air  ensues  the 
flash-point  has  been  reached.  The  flame  is  enlarged,  and  when  the 
temperature  has  increased  io°— 15°  it  is  passed  over  the  surface  at 
every  2°  increase  until  quiet  ignition  takes  place.  The  burning 
point  is  so  obtained.  Draughts  are  prevented  by  screens  of  paste- 
board. 

The  burning  point  of  spindle  oils  should  not  lie  under  150°; 
that  of  machine  oils  (transmission  oils)  not  below  170°. 


PETROLEUM    (ILLUMINATING    OIL).  129 

(//)  Acidity.  Mineral  oils  should  be  entirely  free  from  acids. 
The  acid  remaining  after  the  refining  process  is  detected  by  shak- 
ing about  100  c.c.  oil  with  an  approximately  equal  volume  of  tepid 
water  to  which  several  drops  of  methyl  orange  have  been  added. 
The  aqueous  layer,  after  settling,  will  appear  red. 

(<?)  Resins.  Incompletely  refined  oils  resinify  readily.  A  test 
for  resinous  matter  can  be  conducted  by  placing  20  c.c.  sample,  to- 
gether with  10  c.c.  sulphuric  acid  and  20  c.c.  petroleum  benzine, 
in  a  cylinder  divided  into  50  c.c.,  agitating  and  allowing  to  settle. 
The  increase  in  volume  of  the  sulphuric  acid  is  read  off.  With 
good  oils  the  increase  usually  amounts  to  1.2-2.4  c.c.,  that  is  6—12 
per  cent,  of  the  oil  volume.  Under  no  conditions  must  it  exceed 
2.4  c.c.  (12  per  cent.). 

(/)  Fatty  oils.  Fatty  oils  are  easily  detected  by  the  notice- 
able saponification  number  which  they  possess.  A  quantitative  de- 
termination is  conducted  by  the  method  which  will  be  described 
later  (p.  132). 

(£•)  Rosin  oil.  For  qualitative  purposes  the  test  of  Storch- 
Morauski  is  to  be  recommended:  1-2  c.c.  oil  are  shaken  with 
i  c.c.  acetic  anhydride.  The  liquid  is  allowed  to  settle,  the  acetic 
anhydride  is  pipetted  off  and  treated  with  a  drop  of  sulphuric  acid 
(sp.  gr.  1.53).  In  the  presence  of  rosin  oil  a  violet  color  is  pro- 
duced. The  freezing  point  of  an  oil,  which  in  use  is  subjected  to 
winter  temperature,  is  usually  taken.  Furthermore,  the  lubricating 
value  is  frequently  determined  by  means  of  special  complicated  ap- 
paratus. 

2.  Petroleum  (Illuminating  Oil). 

The  valuation  of  petroleum  as  an  illuminant  is  estimated  by  use 
of  specific  gravity,  flash  point,  viscosity  and  distillation  tests. 

(a)  Specific  gravity.  The  areometer,  less  frequently  the  pyk- 
nometer,  is  used.  Finer  American  oils  have  an  average  specific 
gravity  .800;  Galician  oil  .So5~.82o  ;  and  finer  qualities  Russian 
kerosene  .8i5~.8 20.  In  general,  too  low  a  specific  gravity  indicates 
admixture  with  low-boiling  oils,  and,  in  consequence,  danger  from 
fire.  A  high  specific  gravity  indicates  imperfect  separation  from 
high-boiling  oils.  To  use  specific  gravity  alone  as  a  criterion  is 
altogether  too  unreliable. 

(<£)  Flash  point.     Since  1882  the  apparatus  of  Abel  has  been 


130  CHEMICAL-TECHNICAL   ANALYSIS. 

used  in  the  official  testing  of  petroleum.  It  consists  mainly  of  a 
petroleum  receiver  provided  with  a  lid  and  warmed  externally 
with  a  water-bath.  The  petroleum  is  filled  in  up  to  a  designated 
mark.  A  thermometer  inserted  into  the  lid  is  immersed  in  the 
petroleum.  In  addition  it  is  provided  with  openings  which  can  be 
opened  or  closed  by  a  slide  worked  simultaneously  by  means  of  a 
small  piece  of  mechanism,  with  a  small  lamp  suspended  on  trun- 
nions. As 'the  slide  is  made  to  recede,  the  small  flame  comes  di- 
rectly over  the  middle  opening,  and  is  there  in  direct  contact  with 
the  petroleum  vapors.  As  the  slide  is  made  to  close  the  opening, 
the  flame  recedes.  The  water  in  the  water-bath  is  heated  to  54.5- 
55°.  Continuous  manipulation  is  started  as  soon  as  the  petroleum 
approaches  the  expected  flash  point,  and  is  repeated  for  every  half 
degree  rise  in  temperature  until  a  sudden  flash  of  blue  light  an- 
nounces ignition.  Exact  description  and  instructions  accompany 
the  apparatus,  on  account  of  which  a  closer  description  is  not  ne- 
cessary here.  The  minimum  flash  point  allowed  in  Germany  is 

21°   C. 

(<r)  Viscosity.  According  to  Engler,  the  viscosity  of  illuminat- 
ing oil  bears  a  direct  relation  to  the  speed  of  absorption  in  the 
wick.  To  conveniently  determine  this  speed  in  an  oil,  therefore, 
the  viscosity  is  taken.  The  Engler  apparatus,  possessing,  however, 
a  i. 8  mm.  exit  (instead  of  3  mm.),  is  used. 

(X)  Distillation  test  (distillation  curve).  This  is  conducted  in 
a  distilling  bulb  of  the  following  dimensions  :  Diameter  of  lower 
part  6.5  cm.,  diameter  of  neck  1.6  cm.,  length  of  neck  15  cm. 
The  side  tube  should  be  10  cm.  long,  .6  cm.  wide,  and  attached  at 
an  angle  of  75°.  The  distance  from  the  place  of  attachment  to 
the  level  of  the  100  c.c.  oil,  with  which  the  flask  is  filled,  should 
be  9  cm.  The  side  tube  is  attached  to  a  condenser  of  i  cm.  aver- 
age width  and  45  cm.  length.  100  c.c.  petroleum  are  placed  in 
the  bulb  with  a  pipette  and  are  heated  to  boiling.  A  wire  gauze 
is  set  under  at  first,  but  it  is  removed  when  the  temperature  has  as- 
cended above  150°.  Distillation  is  conducted  so  that  2-2^  c.c. 
distil  every  minute.  The  fractions  between  every  25°  or  50°  are 
weighed  or  measured.  As  soon  as  a  temperature  of  150°  is  reached 
the  temperature  is  allowed  to  sink  at  least  20°  by  removing  the 
lamp.  The  contents  are  again  brought  to  boiling,  and  are  distilled 


PRODUCTS  OF  THE  FAT  INDUSTRY.          131 

until  the  above  temperature  is  again  reached.  This  is  repeated 
until  nothing  more  distils  up  to  that  point.  Results  agreeing  within 
i  per  cent,  are  thus  obtained.  The  main  fraction,  150-300°,  is 
termed  normal  illuminating  oil.  The  amount  of  same  in  especially 
well  refined  illuminating  oils  can  reach  80  and  even  90  volume  per 
cent.  A  good  illuminating  oil  should  contain  (according  to  Beil- 
stein)  not  more  than  about  5  per  cent,  fraction  under  150°  and  not 
more  than  about  15  per  cent,  fraction  above  270°. 

The  test  for  acids  can  be  conducted  according  to  the  method 
described  under  lubricating  oil.  The  behavior  toward  cone,  sul- 
phuric acid  is  at  times  used  as  a  test  for  purity  of  petroleum.  On 
mixing  with  an  equal  volume  of  cone,  sulphuric  acid,  and  allowing 
to  separate,  the  petroleum  layer  should  be  rather  lighter  and  the 
sulphuric  acid  at  the  most  only  yellow,  but  never  brown.  The  rise 
of  temperature  on  mixing  should  not  exceed  5°.  A  rise  of  temper- 
ature of  20—50°  ensues  when  distillates  from  bituminous  shales, 

rosin,  etc.,  are  present. 

3.  Gas  Oil. 

An  approximate  means  of  determining  the  gas  contained  in  gas 
oil  can  be  found  in  a  gasification  on  a  small  scale  by  gasifying  a  defi- 
nite quantity  of  the  oil  in  a  red-hot  retort  into  which  it  is  dropped, 
and  measuring  the  gases  formed.  The  Italian  customs  authorities 
prescribe  the  use  of  the  method  of  Nasini  and  Villavecchia  in  test- 
ing gas  oils.  100  grs.  oil  are  distilled  under  reduced  pressure  (40 
mm.)  to  a  temperature  of  210°  and  the  distillate  so  obtained  is 
distilled  under  normal  pressure  to  310°.  The  fraction  should  not 
exceed  20  per  cent,  of  the  total  oil  used. 

D.  Products  of  the  Fat  Industry. 

1.  Materials  Used  in  Oiling  Wool. 

Fatty  oils,  oleic  acid,  especially  emulsion  of  oil  and  oleic  acid, 
with  small  quantities  of  ammonia  or  soda  and  water,  are  used  for 
this  purpose.  The  fatty  oils  are  also  replaced  in  part  by  mineral 
oils,  due  to  the  fact  that  80  parts  mineral  oil  with  but  10  parts  oleic 
acid  and  10  parts  ^  per  cent,  solution  of  soda  emulsify  very  well. 
Mineral  oil,  when  present,  is  frequently  the  cause  of  spots  in  the 
cloth.  The  oils  from  the  scouring  water  are  also  used  under  the 
names  elam,  extract  oil.  The  examination  of  other  products  em- 


132  CHEMICAL-TECHNICAL   ANALYSIS. 

braces  the  determination  of  unsaponifiable  matter,  neutral  fat,  free 
fatty  acids,  alkali  salts  of  fatty  acids,  and  occasionally  water  and 
alcohol. 

(#)  Unsaponifiable  matter.  Qualitative  test.  A  piece  of  stick 
potash,  pea-size,  is  dissolved  in  5  c.c.  95  per  cent,  alcohol.  Three 
drops  substance  to  be  tested  are  added  and  the  whole  is  boiled  for 
a  minute.  Should  turbidity  ensue  on  addition  of  3  c.c.  water,  un- 
saponifiable matter  is  present. 

Quantitative  determination.  About  10  grs.  substance  are  dis- 
solved in  50  c.c.  95  per  cent,  alcohol,  and  to  this  are  added  3  grs. 
caustic  potash,  dissolved  in  a  very  little  water.  By  heating  with  a 
reflux  on  a  water-bath  for  an  hour,  fatty  acids  and  neutral  fats  are 
saponified.-  It  is  then  diluted  with  30  c.c.  water  and  extracted  in 
a  separatory  funnel  with  petroleum  ether.  Addition  of  alcohol  as- 
sists the  separation  of  the  two  layers.  The  soap  solution  so  ob- 
tained is  run  off  and  extracted  a  few  more  times  with  petroleum 
ether.  The  collected  petroleum  extractions  are  shaken  1—2  times 
with  a  little  water  in  order  to  free  from  dissolved  soap.  The  petro- 
leum ether  is  then  filtered  through  a  dry  filter  into  a  weighed  flask. 
The  solvent  is  then  distilled  off  as  much  as  possible,  and  the  last 
adhering  traces  are  removed  by  immersing  the  flask  in  a  hot  water- 
bath  and  conducting  into  it  a  current  of  air  from  a  blast  bellows. 
After  about  15  minutes  the  flask  is  removed  from  the  water-bath,  is 
allowed  to  cool,  and  weighed.  Air  is  repeatedly  run  through  for 
10  minutes  at  a  time  until  the  weight  of  the  flask  is  nearly  con- 
stant. The  increase  in  weight  represents  the  unsaponifiable  mat- 
ter of  mineral  oil  nature. 

(^)  Total  fatty  acids.  The  soap  solution  contained  in  (#)  is 
decomposed  with  dilute  hydrochloric  acid  and  shaken  out  with  ether 
in  a  separatory  funnel.  The  ether  layer  is  separated,  distilled,  and 
the  fatty  acids  in  the  residue  are  determined  as  in  (a). 

(c]  Free  fatty  acids.  About  10  grs.  sample  are  dissolved  in  50 
c.c.  alcohol  (if  necessary  by  heating)  and  titrated  with  normal 
alkali,  using  phenol -phthalein  as  indicator.  The  amount  of  alkali 
solution  used  is  first  of  all  recorded. 

(d}  Alkalies.  The  alkalies  present  in  form  of  fatty  acid  salts 
are  determined  by  heating  5-10  grs.  sample  with  water,  adding  an 
excess  of  standardized  sulphuric  acid  (about  ^  normal),  separat- 


SOAPS.  133 

ing  from  the  precipitated  fat  (fatty  acids,  neutral  fat,  unsaponifi- 
able  matter)  by  filtration  or  extraction  with  petroleum  ether,  and 
titrating  back  the  excess  of  acid  in  the  aqueous  layer. 

The  nature  of  the  alkali  can  be  qualitatively  proved  in  another 
portion.  Attention  is  also  called  to  the  not  infrequent  presence  of 
ammonium  soaps. 

O)  Mean  molecular  weight  of  the  fatty  acids.  The  determina- 
tion is  necessary  to  determine  the  exact  quantities  of  free  fatty 
acids,  soaps  and  neutral  fats.  For  this  purpose  the  total  fatty  acids 
obtained  as  in  (£)  are  dissolved  in  alcohol  and  titrated  with  normal 
alkali,  using  phenol-phthalein  as  indicator.  Let  g  —  the  weight  of 
fatty  acids,  u  the  number  of  c.c.  normal  alkali  used,  then  M,  the 
mean  molecular  weight,  is  gotten  by  the  formula : 

M=  I00°  g. 
u 

Water  and  alcohol  are  sometimes  present  in  wool  oiling  mate- 
rial. They  are  determined  together  by  placing  about  30  grs. 
ignited  quartz  sand  in  a  platinum  capsule  and  finding  the  weight  of 
capsule  -f-  sand  -f  small  glass  rod.  About  5-  grs.  sample  are 
weighed  out  in  the  dish  and  admixed  by  stirring.  It  is  dried  at 
100°  and  the  loss  of  weight  is  noted. 

Calculation  of  the  quantities  of  free  fatty  acid,  soap  and  neutral 
fat  present : 

(«)  The  amount  of  normal  alkali  used  in  (<:}  is  multiplied  by  the 
quotient  of  1000  into  the  mean  molecular  weight.  The  free  fatty 
acids  are  thus  obtained. 

(/3)  The  quantity  of  alkali  found,  according  to  (//),  is  reck- 
oned into  fatty  acids  present  in  the  form  of  soap,  by  means  of  the 
mean  molecular  weight. 

(>)  If  the  free  acids,  as  found  in  (a),  as  well  as  the  fatty  acids 
found  present  as  soap,  as  in  (/?),  be  subtracted  from  the  total  fatty 
acids,  there  remains  that  which  is  present  as  neutral  fat  and  which 
can  be  reckoned  into  neutral  fat  with  sufficient  accuracy  by  multi- 

100 
plying  by  ---. 

2.  Soaps. 

Soaps  are  mainly  alkali  salts  of  fatty  acids,  in  fact,  sodium  and 
potassium  salts. 


134  CHEMICAL-TECHNICAL    ANALYSIS. 

Soda  soaps  are  hard  and  come  into  the  market  under  the  name  of 
compact  soaps,  cut  or  filled  soaps.  Potash  soaps  are  soft  and  are 
known  as  soft  soaps.  Lately,  however,  hard  potash  soaps  (Schicht's 
patent)  have  appeared.  For  many  industrial  purposes,  substances 
such  as  rosin  (rosin  soaps),  borax,  water-glass,  sodium  alumin- 
ate,  soda  (to  increase  alkalinity),  are  added  to  soaps.  Further- 
more, adulterants,  such  as  chalk,  heavy  spar,  starch,  clay,  etc., 
etc.,  are  frequently  encountered. 

Analysis  of  Pure  Soaps. 

These  may  contain,  beside  the  alkali  salts  of  fatty  acids,  free 
alkali,  alkaline  carbonates,  free  fatty  acids  and  neutral  fats.*  In  ad- 
dition, a  considerable  quantity  of  water  is  always  present. 

(a)  Water.  About  5  grs.  of  soap,  removed  from  the  center, 
in  form  of  shavings,  are  dried  at  50°  for  1-2  hours.  The  temper- 
ature is  then  gradually  raised  to  100-110°  and  the  soap  is  dried  to 
constant  weight. 

Soft  soaps  are  placed  in  a  100  c.c.  beaker  containing  a  small  gl^ss 
rod,  and  the  bottom  of  which  is  covered  1.3  cm.  deep  with  ignited 
quartz  sand.  Beaker  +  sand  +  rod  are  weighed,  f  About  5  grs. 
soap  are  added  and  the  whole  is  reweighed.  25  c.c.  alcohol  are 
added,  and  the  mass  is  heated  on  a  water-bath  and  stirred.  The 
beaker  is  then  placed  in  a  drying  oven  and  dried  to  constant  weight 
at  110°. 

(£)  Total  fat  and  total  alkali. 

10-20  grs.  fine  cut  soap  are  dissolved  in  about  100  c.c.  hot  water 
in  a  beaker.  An  excess  of  standardized  sulphuric  acid  is  added  (50— 
80  c.c.  normal  acid)  and  the  whole  is  heated  in  a  water-bath  con- 
taining boiling  water  until  a  clear  layer  of  fatty  acids  is  formed.  It 
is  now  allowed  to  cool.  In  case  the  fatty  acids  refuse  to  solidify 
a  weighed  quantity  of  wax,  paraffin  or  stearic  acid,  approximately 
equal  in  weight  to  the  soap  taken,  is  added,  and  the  mass  is  re- 
heated and  again  allowed  to  cool.  The  fatty  acid  cake,  now  solid, 
is  removed  from  the  beaker  with  a  glass  rod,  and  is  washed  off  with 
water.  The  washings  are  caught  in  the  beaker.  It  is  externally 

*  Manifestly,  a  simultaneous  presence  of  free  alkali  and  free  fatty  acid  is  im- 
possible. 

f  All  weighings  should  be  made  as  nearly  as  possible  at  the  same  time,  because 
the  quantity  of  water  in  soaps  readily  changes. 


SOAPS.  135 

dried  with  filter  paper  and  kept  in  a  cool  place.  The  solution  re- 
maining in  the  beaker  is  filtered,  the  filter  is  washed  well,  and  the 
filtrate  is  titrated  back,  using  methyl  orange  as  an  indicator.  The 
total  alkali,  representing  that  combined  with  fatty  acids,  free  alkali 
and  alkaline  carbonates,  is  calculated  from  the  acid  required  for 
decomposition. 

The  total  fat  is  determined  by  dissolving  the  particles  adhering 
to  the  beaker  in  ether,  filtering  the  latter  through  the  previously  em- 
ployed filter  into  a  weighed  glass  vessel  containing  a  glass  rod.  After 
the  ether  has  been  volatilized,  the  fatty  acid  cake  is  also  placed  in 
the  vessel  and  is  heated  with  a  small  flame,  with  constant  stirring, 
until  the  crackling  sound,  caused  by  escaping  steam,  has  ceased, 
and  the  vapors  of  fatty  acids  have  begun  to  make  their  appearance. 
Upon  cooling,  the  glass  dish  is  weighed  and  the  added  paraffin, 
etc. ,  is  deducted.  The  total  fat  is  thus  obtained.  Any  neutral  fats, 
as  well  as  fatty  acids,  will  be  present. 

(c)  Alkaline  carbonates  and  free  alkali. 

Qualitative  test. — A  portion  of  soap  is  warmed  and  dissolved  in 
alcohol,  filtered,  and  any  residue  is  wrashed  with  alcohol.  Free 
alkali  is  detected  by  the  red  color  which  will  form  on  addition  of 
phenol-phthalein  to  the  filtrate.  On  the  other  hand,  the  residue 
on  the  filter  is  dissolved  in  water  and  tested  for  alkaline  carbon- 
ates by  warming  with  phenol-phthalein. 

Quantitative  determination. — About  10  grs.  soap  are  treated  as 
above,  care  being  taken,  however,  in  washing  with  the  alcohol, 
which  is  best  done  by  using  a  hot  water  funnel  during  filtration. 

The  alcoholic  filtrate,  as  well  as  the  aqueous  solution  of  the  well- 
washed  residue,  is  titrated  with  ^  normal  acid,  using  phenol-phthal- 
ein as  indicator  in  the  first  instance  and  methyl  orange  in  the 
second. 

After  the  free  alkali  and  alkali  carbonate  have  been  deducted  from 
the  total  alkali  found,  as  in  (^)  (everything  calculated  as  alkali  ox- 
ide), there  remains  the  alkali  which  is  bound  to  the  fatty  acids. 
This  can  also  be  directly  determined  by  dissolving  a  weighed  quan- 
tity of  soap  in  water,  decomposing  it  with  an  excess  of  hydro- 
chloric acid,  thus  using  the  separated  fat  in  a  moistened  filter, 
washing,  dissolving  the  fatty  acid  in  alcohol  by  placing  filter  and 
contents  in  a  beaker  with  alcohol,  and  finally  titrating  with  alkali, 
using  phenol-phthalein  as  indicator. 


136  CHEMICAL-TECHNICAL    ANALYSIS. 

As  a  rule  the  alkali  in  hard  soaps  is  calculated  as  sodium  oxide 
and  that  of  soft  soaps  as  potassium  oxide.  On  the  assumption  that 
both  potash  and  soda  are  present  in  a  soap,  5  grs.  of  the  latter  are 
burned  in  a  platinum  dish  until  only  a  charred  mass  remains.  This 
is  covered  with  water,  filtered  and  washed.  In  the  aqueous  filtrate 
a  check  determination  of  total  alkali  may  be  conducted  by  titration 
with  hydrochloric  acid,  after  which  a  determination  of  potassium 
is  made  in  the  usual  way  with  platinic  chloride.  (See  Fertilizers, 

P-  73-) 

(*/)  Free  fatty  acids.  When  the  alcoholic  soap  solution  does 
not  change  color  on  addition  of  phenol-phthalein  (a  proof  of  the 
absence  of  free  alkali),  free  acid,  which  may  be  present,  can  be  de- 
termined by  titration  with  caustic  soda. 

(>)  Neutral  fat.  A  considerable  quantity  of  fine  shaved  soap  is 
weighed  off,  dried  and  extracted  in  a  Soxhlet  extractor  with  ether. 
In  order  to  remove  traces  of  soap  which  may  perchance  have  gone 
into  solution,  the  ethereal  extract  is  shaken  out  2—3  times  with 
water  in  a  separatory  funnel.  Then,  if  necessary,  it  is  filtered,  the 
ether  is  volatilized,  and  the  residue  is  weighed  after  the  usual  treat- 
ment in  a  current  of  air.  It  also  contains  any  free  fatty  acids 
which  may  have  been  present.  The  latter  may  be  deducted  after 
determination  (//)  has  been  made,  or  they  may  be  directly  titrated. 

Summary  of  analysis. — The  percentage  of  fatty  acids  must  not  be 
placed  as  such  in  the  analysis,  but  must  first  be  reckoned  into 
anhydrides.  No  great  error  is  experienced  in  simply  deducting 
3.25  per  cent,  from  every  100  parts  fatty  acid.* 

In  order  to  ascertain  the  nature  of  the  fat  from  which  a  soap  has 
been  made  the  separated  fatty  acids  are  tested  for  melting  point, 
freezing  point,  specific  gravity,  iodine  number,  saponification  num- 
ber, etc. 

Determination  of  Foreign  Admixtures  in  Soaps. 

(a}   Examination  of  residue  insoluble  in  alcohol. 

To  determine  the  total  amount  of  the  same,  a  weighed  quan- 
tity of  soap  is  dried  and  warmed  on  a  water-bath  with  8-10 
times  the  quantity  of  alcohol.  It  is  then  filtered  through  a  weighed 


*  Instead  of  this  a  quantity  of  water,  equivalent  to  the  alkali  which  is  bound  to 
fatty  acids,  may  be  deducted. 


SOAPS.  137 

filter,  washed  with  alcohol,  dried  and  weighed.  The  residue  is  ex- 
tracted with  cold  water  and  the  solution  is  tested  for  chlorides,  sul- 
phates, carbonates,  silicates  and  borates  of  the  alkalies.  If  neces- 
sary, quantitative  determinations  of  these  constituents  may  be  made 
in  the  usual  manner. 

The  residue  from  the  aqueous  extraction  is  ignited  to  destroy  or- 
ganic matter,  is  weighed,  and  the  ash  is  qualitatively  and  quantita- 
tively examined.  It  is  advisedly  examined  for  chalk,  clay,  in- 
fusorial earth,  etc. 

Any  organic  matter,  such  as  dextrine,  contained  perhaps  in  the 
residue  from  the  alcohol  extraction,  is  dissolved  in  cold  water  and 
can  be  reprecipitated  from  its  aqueous  solution  by  alcohol.  Starch 
can  be  detected  under  the  microscope  as  well  as  by  the  blue  colora- 
tion with  iodine. 

(£)  Glycerin,  quantitative  estimation,  i-io  grs.  soap  are  dis- 
solved in  water  or  in  methyl  alcohol  when  organic  substances,  in- 
soluble in  methyl  alcohol,  are  present.  The  solution  is  filtered, 
the  alcohol  is  volatilized,  the  fatty  acids  are  separated  with  dilute 
hydrochloric  acid,  and  the  glycerin  in  the  acid  filtrate  is  estimated 
according  to  the  method  of  Benedikt  and  Zsigmondy.  (See  Gly- 
cerin, p.  141.) 

(V)  Rosin.  In  the  qualitative  test  for  rosin  in  soaps,  or  in  the 
fatty  acids  separated  from  the  latter,  the  reaction  of  Storch  and 
Morowski  (p.  129)  is  used.  The  method  used  in  the  quantitative 
estimation  of  rosin  in  the  mixture  of  the  latter  with  fatty  acids, 
which  is  separated  by  mineral  acids,  has,  until  recently,  been  that 
of  Gladding.  It  depends  on  the  fact  that  the  silver  salts  of  fatty 
acids  are  insoluble  in  ether,  whereas  silver  resinate  is  soluble  in 
the  latter.  Lately  preference  has  been  given  the  method  of  Twitchell. 
It  depends  on  the  property  of  fatty  acids  forming  esters  when 
hydrochloric  acid  gas  is  conducted  into  their  solution,  whereas 
rosin  does  not  react  under  the  same  conditions. 

2-3  grams  rosin-fatty  acid  mixture  are  dissolved  in  10  times  the 
volume  of  absolute  alcohol  in  a  flask.  A  brisk  current  of  hydro- 
chloric acid  gas  is  led  in.  Meanwhile,  the  temperature  is  kept  under 
20°  by  good  cooling.  At  first  the  gas  is  rapidly  absorbed.  After 
a  period  of  about  %  of  an  hour  the  esters  formed  separate  on  the 
surface  and  further  absorption  ceases.  The  flask  is  withdrawn  from 


138  CHEMICAL-TECHNICAL    ANALYSIS. 

the  cooling  mixture,  is  allowed  to  stand  ^  hour,  is  diluted  with  5 
times  the  volume  of  water,  and  boiled  until  the  acid  solution  clari- 
fies. The  resinic  acids  can  be  determined  either  gravimetrically  or 
volumetrically. 

(a)  Gravimetric  method.  The  contents  of  the  flask  are  placed 
in  a  separatory  funnel  and  shaken  up  with  petroleum  ether.  The 
acid  layer  is  drawn  off,  the  petroleum  ether  layer  is  washed  and 
shaken  up  with  a  solution  of  5  grs.  caustic  potash,  dissolved  in  5 
c.c.  alcohol  and  50  c.c.  water.  The  resin  is  saponified  and  the  soap 
formed  remains  dissolved  in  the  aqueous  layer  which  separates  com- 
pletely from  the  petroleum  ether  layer.  The  soap  solution  is  drawn 
off  and  the  petroleum  ether  is  washed  first  with  dilute  potassium 
hydrate  solution  and  then  with  water. 

The  collected  aqueous  extractions  are  decomposed  with  dilute 
hydrochloric  acid.  The  precipitated  resinic  acids  are  dissolved  in 
ether,  the  ether  is  distilled  off,  and  the  residue  is  dried  at  100° 
and  weighed. 

(/5)  Volumetric  method.  The  contents  of  the  flask  are  shaken 
up  with  about  75  c.c.  ether  in  a  separatory  funnel,  the  acid  layer  is 
drawn  off,  and  the  etherial  layer  is  washed  with  water  until  acid  re- 
action with  litmus  paper  has  ceased.  50  c.c.  alcohol  are  added 
and  the  solution  is  titrated  with  ^  normal  alkali,  using  phenol - 
phthalein  as  indicator.  The  resinic  acids  are  saponified,  whereas 
the  fatty  esters  remain  unattacked.  The  resinic  acid  equivalent  is 
taken  as  346  in  the  calculation. 

3.   Turkey-Bed  Oil. 

Turkey-red  oil  is  a  product  of  reaction  between  concentrated 
sulphuric  acid  and  chilled  castor  oil,*  to  which  ammonia  has  been 
added  in  quantity  sufficient  to  impart  the  property  of  forming  a 
complete  emulsion  when  a  sample  is  shaken  with  water.  Turkey- 
red  oil  contains  a  water-soluble  constituent  consisting  of  "  ricinol- 
sulphuric  acid,"  and  which  can  be  salted  out  of  its  aqueous  solu- 
tion with  salt,  very  dilute  sulphuric  acid  and  hydrochloric  acid. 
The  "  ricinoleic  sulphonic  "  acid  is  not  decomposed  by  boiling 
water  or  alkali  solutions,  whereas,  when  boiled  with  dilute  acids,  it 

*  Sometimes  other  oils. 


TURKEY-RED    OIL.  139 

is  converted  into  ricinoleic  acid  and  sulphuric  acid.  That  portion 
of  turkey-red  oil  which  is  insoluble  in  water  consists  mainly  of 
ricinoleic  acid,  and  contains,  in  addition,  some  neutral  fat,  and  per- 
haps polyricinoleic  acids,  together  with  anhydrides  of  ricinoleic 
acid  and  the  above  mentioned  acids.  Good  castor  oil  should  yield 
a  fairly  permanent  emulsion  with  water,  should  dissolve  to  a  clear 
solution  in  ammonia,  and  should  not  become  turbid  thereafter  on 
addition  of  much  water. 

Chemical  Examination. 

According  to  Benedikt,  this  applies  principally  to  the  determin- 
ation of  total  fat.  In  more  exact  analyses,  the  neutral  fat,  sulphonic 
acid,  ammonia,  soda  and  sulphuric  acid  are  determined  by  the 
methods  employed  by  the  above  author. 

(a)  Total  fat.  By  this  is  understood  the  sum  of  the  water-insol- 
uble constituents  of  the  acidified  oil  (fatty  acids,  oxy  fatty  acids 
and  neutral  fat)  and  the  oxy  fatty  acids  obtained  by  the  decomposi- 
tion of  the  soluble  fatty  sulphonic  acids.  About  4  grs.  sample  are 
stirred  with  20  c.c.  water,  which  are  gradually  added,  in  a  thin 
hemispherical  glass  dish  of  about  125  c.c.  capacity,  which  has  pre- 
viously been  weighed,  together  with  a  small  glass  rod.  When  the 
liquid  is  turbid,  a  drop  of  phenol -phthalein  is  added,  followed  by 
ammonia  to  faint  alkaline  reaction.  It  is  now  mixed  with  15  c.c. 
of  sulphuric  acid,  is  diluted  with  an  equal  volume  of  water  and 
6—8  grs.  stearic  acid  are  added,  whereupon  it  is  heated  to  faint 
ebullition.  When  the  fatty  acids  have  separated  in  a  clear  layer, 
it  is  allowed  to  cool.  The  solid  cake  is  raised  with  a  glass  rod, 
rinsed  with  water,  and  placed  on  filter  paper.  The  fat  particles 
attached  to  the  walls  are  collected  by  heating  the  liquid  in  the  dish 
until  the  particles  have  united  to  i  or  2  drops.  The  dish  is  re- 
moved from  the  water-bath  and  inclined,  so  that  the  drops  reach 
the  glass  walls,  where  they  immediately  solidify  and  cling.  The 
liquid  is  now  poured  off,  the  fat  cake  is  placed  in  the  rinsed  dish 
and  heated  with  a  small  flame  in  a  manner  similar  to  that  employed 
in  the  total  fat  estimation  in  soap  (p.  134).  The  cooled-off  cake 
residue  is  weighed  and  the  weight  of  stearic  acid  added  is  deducted. 

(^)  Neutral  fat.  About  30  grs.  sample  are  dissolved  in  50  c.c. 
water,  20  c.c.  ammonia  and  30  c.c.  glycerin  are  added,  and  the 
mass  is  shaken  out  twice  with  quantities  of  100  c.c.  ether.  Small 


140  CHEMICAL-TECHNICAL    ANALYSIS. 

traces  of  soap,  which  are  taken  up  by  the  ether,  are  removed  by 
shaking  with  water.  The  ether  is  then  distilled  off  and  the  residue 
is  dried  first  in  a  water-bath,  then  in  an  air-bath,  and  is  finally 
weighed. 

(t~)  Soluble  fatty  acids.  (Fatty  sulphonic  acids.)  5-10  grs. 
sample  are  dissolved  in  25  c.c.  water  in  a  pressure  flask.  25  c.c. 
fuming  hydrochloric  acid  are  added,  and  the  flask  is  heated  in  an 
oil-bath  at  130—150°  for  an  hour.  Its  contents  are  then  diluted 
with  water,  poured  into  a  beaker  and  filtered  from  the  fat  layer. 
To  insure  easy  manipulation  an  indefinite  quantity  of  stearic  acid 
may  be  added,  the  solution  heated,  and  again  allowed  to  cool.  A 
sulphuric  acid  determination  is  made  in  the  filtrate  by  means  of 
barium  chloride.  The  sulphuric  acid  found  in  (<?)  is  deducted 
from  this,  and  the  remainder  is  calculated  into  ricinol-sulphuric 
acid.  (80  parts  sulphuric  acid  correspond  to  378  parts  ricinol- 
sulphuric  acid.) 

(</)  Ammonia  and  soda.  15-20  grs.  oil  are  dissolved  in  ether 
and  shaken  out  4  times  with  quantities  of  5  c.c.  dilute  sulphuric 
acid.  A  part  of  the  collected  extractions  is  distilled  with  potas- 
sium hydrate  to  determine  ammonia,  and  in  another  portion  the 
soda  is  determined  as  sodium  sulphate.  This  is  obtained  by  evap- 
orating the  solution  on  a  water-bath,  volatilizing  the  sulphuric  acid, 
and  igniting  the  residue  with  additions  of  ammonium  carbonate. 

(e)  Sulphuric  acid.  The  sulphuric  acid  present  in  form  of  sul- 
phate of  ammonia  or  soda  is  determined  by  shaking  the  ethereal 
solution  of  the  oils  several  times  with  small  quantities  of  a  saturated 
solution  of  salt,  which  is  free  from  sulphuric  acid.  The  collected, 
diluted  and  filtered  extractions  are  precipitated  with  barium  chlo- 
ride. When  an  insight  into  the  source  of  a  turkey -red  oil  is  de- 
sired, especially  whether  the  substance  in  question  is  a  castor  oil 
turkey -red  oil,  the  iodine  number  and  acetyl  number  are  taken  of 
the  total  fats  (#),  to  which,  however,  no  stearic  acid  has  been 
added. 

An  iodine  number  considerably  under  70  and  an  acetyl  number 
under  140  indicate  admixture  with  other  oils. 

4.  Glycerin. 

(a)  Crude  glycerin.  For  determination  of  glycerin  in  crude 
glycerin  the  acetin  method  is  preferred.  It  depends  on  the  phe- 


GLYCERIN.  141 

nomenon  that  glycerin  on  boiling  with  acetic  anhydride  is  quanti- 
tatively transformed  into  triacetin.  If  the  latter  be  then  dissolved 
in  water,  and  the  free  acetic  acid  be  neutralized  with  sodium  hy- 
drate, the  dissolved  triacetin  can  be  saponified  with  caustic  soda 
and  the  excess  of  the  latter  titrated  back. 

The  necessary  reagents  are  : 

(«)  ^  normal  to  normal  hydrochloric  acid  accurately  standard- 
ized. 

(/?)  Dilute  alkali,  not  standardized,  which  contains  not  more 
than  20  grs.  sodium  hydrate  to  the  liter. 

(/)  Concentrated,  about  10  per  cent,  alkali,  best  preserved  in  a 
flask  provided  with  a  25  c.c.  pipette,  i— 1.5  grs.  sample  are 
weighed  out  in  a  wide-necked,  small,  round-bottom  flask  of  about 
100  c.c.  capacity.  7-8  grs.  acetic  anhydride  are  added,  with  about 
3  grs.  dehydrated  acetate  of  soda.  The  mass  is  boiled  on  a  reflux 
for  i—ij4  hours.  It  is  then  allowed  to  cool  somewhat,  is  diluted 
with  50  c.c"  water,  and  likewise  heated  on  a  reflux  until  the  oil  is 
completely  dissolved.  The  solution  is  now  filtered  into  a  400—600 
c.  c.  wide-necked  flask.  Usually  a  copious  flocculent  white  precipitate 
remains  on  the  filter.  The  solution  is  allowed  to  cool,  phenol- 
phthalein  is  added,  after  which  it  is  neutralized  exactly  with  dilute 
alkali.  This  is  accomplished  when  the  yellow  color  changes  to 
reddish  yellow.  Dilute  acid  and  cold  solution  must  be  used,  as 
otherwise  the  triacetin  will  be  saponified.  25  c.c.  of  the  concen- 
trated 10  per  cent,  alkali  is  then  added  from  the  pipette.  The 
final  adhering  drops  are  counted  the  same  for  each  experiment.  It 
is  boiled  for  a  quarter  of  an  hour  and  titrated  back  with  hydro- 
chloric acid.  Exactly  the  same  amount  (25  c.c.)  of  alkali  is  then 
titrated  with  the  hydrochloric  acid,  and  from  the  difference  the 
alkali  used  by  the  triacetin  is  found.  This  is  then  calculated  into 
glycerin.  (3  molecules  NaOH  represent  i  molecule  glycerin.) 

(£)   Determination  of  glycerin  in  fats  and  soaps. 

When  glycerin  in  strongly  alkaline  solution  is  oxidized  at  ordi- 
nary temperature  with  potassium  permanganate,  it  is  completely 
transformed  into  oxalic  acid  : 

C3H803+302  =  C2Hp4+C02+3H20. 

On  this  reaction  rests  the  method  of  Benedikt  and  Zsigmondy, 
which  will  be  described  here  in  the  modified  form  of  Herbig  and 
Mangold. 


142  CHEMICAL-TECHNICAL    ANALYSIS. 

2-3  grs.  fat  are  saponified  in  pure  methyl  alcohol  with  potassium 
hydrate.  The  alcohol  is  volatilized,  the  residual  soap  is  dissolved 
in  hot  water  and  is  decomposed  with  dilute  hydrochloric  acid.  It 
is  then  heated  until  the  separated  fatty  acids  form  a  clear  layer. 
To  liquid  fat  some  paraffin  had  best  be  added.  It  is  cooled 
thoroughly,  filtered  off  into  a  liter  flask,  and  washed  well.  With 
soaps,  the  method  described  (p.  137)  is  followed  up  to  this  point. 
The  solution  is  exactly  neutralized  with  caustic  potash  and  phenol- 
phthalein.  10  grs.  more  caustic  potash  are  added,  and  as  much  5 
per  cent,  potassium  permanganate  solution  is  added  in  the  cold  as 
would  represent  approximately  i^  times  the  theoretical  amount. 
(For  every  part  glycerin  6.87  parts  potassium  permanganate.) 

The  liquid  will  then  no  longer  appear  green,  but  blue  or  black. 
It  is  allowed  to  stand  ^  hour  at  ordinary  temperature.  Hydrogen 
peroxide,  in  not  too  great  an  excess,  is  added,  until  the  supernatant 
liquid  becomes  colorless.  It  is  diluted  to  the  mark,  is  shaken 
briskly,  and  500  c.c.  are  filtered  off  through  a  dry  filter.  To  de- 
compose the  hydrogen  peroxide  the  liquid  is  boiled  for  ^  hour, 
cooled  to  about  60°,  and  after  addition  of  sulphuric  acid  the  oxalic 
acid  formed  is  titrated  with  permanganate. 

In  place  of  filtration,  the  filtrate,  after  acidifying  with  acetic 
acid,  may  be  precipitated  with  calcium  chloride.  When  filtered  it 
may  be  determined  either  gravimetrically  by  ignition  to  calcium 
oxide,  or  it  may,  after  decomposition  with  sulphuric  acid,  be  titrated 
with  permanganate,  as  above. 


IX.  Mordants  and  Tanning  Materials. 


A.  Mordants. 

THE  substances  which  are  most  used  for  mordanting  are  com- 
pounds of  aluminium,  chromium,  iron,  tin,  antimony  and  copper. 

1.  Alumina  Mordants. 

To  these  belong  sulphate  of  aluminium,  alum,  sodium  aluminate, 
aluminium  acetate. 

(a)  Sulphate  of  aluminium  A12(SO4)3  -f  i8H,O.  This  is  prin- 
cipally examined  for  iron  and  free  sulphuric  acid. 

The  qualitative  test  is  the  red  color  produced  by  a  sulphocyanide 
of  potassium  solution.  The  latter  is  added  to  the  solution  of  the 
sample,  which  has  been  oxidized  with  a  little  nitric  acid.  Lunge* 
states  that  the  method  may  be  advantageously  employed  for  the 
colorimetric  determination  of  iron. 

To  conduct  this  there  are  necessary  (a)  a  10  per  cent,  potassium 
sulphocyanide  solution,  (/?)  pure  ether,  (y)  an  ammonium  alum  solu- 
tion, containing  8.606  grs.  iron  alum  and  6  c.c.  pure  cone,  sulphuric 
acid  to  the  liter.  For  the  experiment  i  c.c.  of  this  solution,  di- 
luted to  100  c.c.,  is  used.  This  dilute  solution  contains  .01  gr. 
iron  in  a  liter,  (d)  pure  nitric  acid  free  from  iron,  (?)  several  cylin- 
ders for  shaking.  These  are  divided  in  T\j  c.c.  to  25  c.c.,  and 
should  have  about  5  c.c.  free  space  above  this.  They  should  be 
nearly  alike  in  height  and  diameter. 

When  small  quantities  of  iron  only  are  present,  as  is  usually  the 
case  with  good  commercial  material,  1-2  grs.  of  the  aluminium  sul- 
phate under  examination  are  dissolved  in  a  little  water  and  exactly 
i  c.c.  nitric  acid  (d)  is  added.  The  solution  is  heated,  allowed  to 
cool,  and  is  diluted  to  50  c.c.  At  the  same  time  i  c.c.  nitric  acid 
(<$)  is  diluted  alone  to  50  c.c.  with  water.  Exactly  5  c.c.  alumin- 

*  Zeitschrift  fur  angewandte  Chem.,  Jahrg.  1894,  p.  669,  and  1896,  p.  3. 


144  CHEMICAL-TECHNICAL   ANALYSIS. 

ium  sulphate  solution  in  question  are  placed  in  one  cylinder  (A}, 
and  in  the  other  cylinder  (.Z?)  are  placed  5  c.c.  of  the  diluted  ni- 
tric acid.  A  quantity,  say  i  c.c.,  dilute  iron  solution  (})  is  added 
to  the  latter,  and  the  same  quantity  of  water  is  added  to  (A)  in 
order  to  preserve  the  same  dilution.  Thereupon  5  c.c.  sulpho- 
cyanide  solution  («)  are  added  to  each  cylinder,  followed  by  10 
c.c.  ether  (/3),  the  stoppers  are  inserted,  and  the  cylinders  vig- 
orously shaken  until  the  aqueous  layer  has  become  colorless. 

The  intensity  of  the  colors  of  the  ethereal  layers  are  thereupon 
compared.  Rough  differences  can  be  instantly  observed.  At  the 
same  time,  one  or  more  tests  are  made  with  greater  or  smaller 
amounts  of  the  diluted  iron  dilution.  When  shades  are  about 
alike,  the  comparisons  are  best  made  after  standing  a  few  hours. 
The  accuracy  can  be  easily  brought  to  ±  .1  c.c.  iron  alum  solution, 
however,  only  when  the  total  iron  present  is  equivalent  to  the  iron 
in  2  c.c.  iron  alum  solution  at  the  most.  For  the  purpose  of  com- 
parison, observation  had  best  be  made  in  transmitted  light,  prefer- 
ably from  above,  through  the  entire  column  of  ether.  To  this  end 
the  cylinder  is  placed  on  a  white  foundation.  Should  the  sulphate 
of  aluminium  contain  a  large  amount  of  iron,  a  considerably  more 
dilute  solution  must  be  used  for  examination.  When  about  ^  per 
cent,  iron  is  present  (the  maximum  amount  allowed  in  use  of  the  col- 
orimetric  method),  only  .  2  gr.  sample  is  dissolved  in  250  c.c.  5  c.c. 
of  this  solution  (=  .004  gr.  sample)  are  used  in  the  experiment. 

Free  sulphuric  acid  is  qualitatively  tested  for  by  treating  the 
powdered  and  dried  substance  with  10  times  its  weight  of  absolute 
alcohol,  whereby  the  free  acid  is  extracted  by  the  alcohol,  in  which 
it  may  be  recognized  by  means  of  litmus  paper.  An  approximate 
quantitative  result  is  obtained  by  titration  with  T^  normal  alkali. 
A  frequently  required  exact  quantitative  estimation  of  the  free  sul- 
phuric acid  is  made  by  dissolving  1-2'  grs.  aluminium  sulphate  in 
5  c.c.  water.  5  c.c.  neutral  saturated  ammonium  sulphate  solu- 
tion are  added,  and  the  mixture  is  stirred  frequently  during  an  in- 
terval of  one  quarter  of  an  hour.  Thereupon  the  entire  aluminium 
sulphate  is  precipitated  in  the  form  of  ammonium  alum  by  the 
addition  of  50  c.c.  95  per  cent,  alcohol,  whereas  the  entire  free 
sulphuric  acid  remains  in  solution.  The  solution  is  filtered.  The 
residue  is  washed  with  50  c.c.  95  per  cent,  alcohol,  the  filtrate  is 


CHROMIUM    MORDANTS.  145 

evaporated  on  a  water-bath,  and  the  residue,  dissolved  in  water,  is 
titrated  with  T\j-  normal  alkali. 

(£)  Alum.  The  examination  for  iron  oxide  and  free  sulphuric 
acid  is  conducted  as  in  (0).  Direct  extraction  of  sulphuric  acid 
with  alcohol  can,  however,  be  resorted  to  in  the  latter  determina- 
tion. Large  quantities  of  sodium  alum  can  be  detected  in  the  pres- 
ence of  potassium  alum  by  the  greater  solubility  of  the  former  in 
water.  (Sodium  alum  dissolves  in  2  parts  water ;  potassium  alum 
in  10  parts  water.)  Potassium  alum  K2SO4.  A12(SOJ8  -f  24  H2O 
and  sodium  alum  Na2SO4.  A12(SO4)3  -f  24  H2O  are  principally  used. 

(V)  Sodium  aluminate.  The  examination  according  to  Lunge 
was  described  in  Chapter  I.,  p.  17. 

(//)  Aluminium  acetate.  Alumina  is  determined  in  the  usual 
manner.  The  estimation  of  acetic  acid  is  made  by  distilling  with 
phosphoric  acid  and  titrating  the  distillate  with  normal  alkali,  using 
phenol -phthalein  as  indicator. 

2.  Chromium  Mordants. 

Potassium  and  sodium  bichromates  are  most  frequently  used  ;  the 
fluoride  comes  next,  whereas  chrome-alum  is  less  frequently  used. 

(#)  Potassium  and  sodium  bichromates.  In  both  materials  the 
chromic  acid  is  determined,  as  well  as  the  sulphates,  which  frequently 
occur  in  sodium  bichromate. 

(a)  Chromic  acid.  The  estimation  is  conducted  either  volu- 
metrically,  preferably  iodometrically,  or  gravimetrically,  by  pre- 
cipitation with  ammonia  after  the  reduction  of  the  chromic  acid 
with  hydrochloric  acid  and  alcohol. 

(/?)  Sulphuric  acid.  The  solution  reduced,  as  directed  above, 
is  precipitated  with  ammonia,  and  the  sulphuric  acid  in  the  filtrate 
is  precipitated  with  barium  chloride. 

In  potassium  bichromate  the  sulphuric  acid  is  present  as  potas- 
sium sulphate,  and  in  sodium  bichromate  as  sodium  sulphate. 

(£)  Fluoride  of  chromium.  Chromium  is  determined  by  pre- 
cipitation with  ammonia. 

(c)  Chromium  alum.  As  impurities  it  fnay  contain  organic 
matter,  tarry  matter,  gypsum  and  sulphate  of  sodium  in  considerable 
quantities. 

10 


146  CHEMICAL-TECHNICAL    ANALYSIS. 

3.  Iron  Mordants. 

These  are  used  in  form  of  ferrous  and  ferric  mordants  ;  in  fact, 
as  green  vitriol  in  the  first  instance,  and  as  ferric  nitrate  containing 
basic  ferric  sulphate,  produced  by  the  oxidation  of  the  ferrous  sul- 
phate by  nitric  acid  in  the  latter  instance. 

In  both  instances  a  determination  of  total  iron  is  made  by  pre- 
cipitation with  ammonia  after  oxidation  with  nitric  acid,  and  a  de- 
termination of  ferrous  oxide  by  titration  with  permanganate  in  sul- 
phuric acid  solution. 

In  the  ferric  nitrate,  furthermore,  the  sulphuric  acid  is  estimated 
with  chloride  of  barium  after  precipitation  of  the  iron  with  ammonia 
and  the  nitric  acid  is  estimated  by  the  usual  methods. 

4.  Tin  Mordants. 

Both  stannous  chloride  (tin  salt)  SnCl2-f  2H2O  and  stannic 
chloride  SnCl4  are  used. 

(#)  Stannous  chloride.  Pure  tin  salt  dissolves  completely  in  5 
times  its  weight  of  absolute  alcohol ;  the  oxidized  salt  gives  a  fine 
pulverous  or  flocculent  precipitate,  which  dissolves  on  addition  of 
alcoholic  hydrochloric  acid.  Adulterants  remain  in  the  form  of 
crystalline  fragments. 

Stannous  oxide  (stannous  chloride).  Method  of  Goppelsoder 
and  Trechsel,  modified  by  FraenkeL* 

3-4  grs.  tin  salt  are  dissolved  in  30-40  c.c.  10  per  cent,  hydro- 
chloric acid  and  diluted  to  500  c.c.  50  c.c.  solution  and  50  c.c 
one-tenth  normal  potassium  bichromate  solution  are  placed  in  a 
stoppered  flask,  and  after  15  minutes  10—15  c-c-  potassium  iodide 
solution  and  5—10  c.c.  hydrochloric  acid  (both  i  :  10)  are  added. 
After  a  half-hour  action  it  is  diluted  with  about  200  c.c.  water, 
and  the  precipitated  iodine  is  titrated  back  with  one-tenth  normal 
hyposulphite  solution.  The  stannous  salt  is  calculated  from  the 
difference  in  c.c.  between  the  bichromate  added  and  the  hyposul- 
phite used  in  back  titration.  i  SnCl2  =  i  SnO  =  2  I.  When 
exactly  one-tenth  normal  solutions  are  used,  the  difference  need 
only  be  multiplied  by  .01125  and  calculated  into  per  cent,  in 
order  to  obtain  the  amount  of  crystallized  tin  chloride  present. 
(SnCl2+2  H20.) 

*  Contribution  from  the  K.  K.  tech.  Gewerbe- Museum,  1892.     Volume  7. 


TANNING    MATERIALS.  147 

(£)  Tin  chloride.  This  comes  into  the  market  in  solid  form  or 
in  form  of  solutions  containing  10-20  per  cent.  tin.  It  is  to  be 
tested  particularly  for  iron  and  nitric  acid.  Stannous  chloride  is 
detected  by  means  of  mercuric  chloride.  Total  tin,  .5-1  gr.  salt 
or  2—4  c.c.  solution  are  diluted  to  100—200  c,c.  with  water,  and 
in  case  stannous  chloride  is  present  a  weak  iodine  solution  is  added 
to  yellow  coloration.  Ammonia  is  then  added  until  the  solution 
faintly  opalesces,  after  which  the  tin  is  precipitated  with  an  excess 
of  a  saturated  solution  of  Glauber  salt.  The  liquid  is  heated  to 
boiling  for  a  while  and  the  voluminous  precipitate  is  decanted  sev- 
eral times  with  hot  water.  It  is  then  thrown  on  a  filter,  is  thor- 
oughly washed,  ignited,  and  weighed  as  tin  oxide. 

5.  Antimony  Mordants. 

Chiefly  to  be  considered  are :  Tartar  emetic  (potassium  anti- 
monyl  tartrate)  K.SbO.C4H4O6  -f  %H2O  and  De  Haen's  salt 
Sb  F13.  (NH4)2  SO4.  The  potassium  antimony  oxalate  has  been 
used  very  little  recently. 

An  antimony  determination  suffices  as  a  rule.  This  is  conducted 
gravimetrically  in  the  usual  manner  by  precipitation  with  hydrogen 
sulphide.  A  volumetric  method  consists  of  tit  ration  with  iodine 
solution:  .5  gr.  sample  is  dissolved  in  about  50  c.c.  water  and 
made  slightly  alkaline  with  bicarbonate  of  soda  solution.  A  pre- 
cipitate which  might  form  is  removed  by  addition  of  Seignette  salt. 
Starch  paste  is  then  added  to  the  solution,  which  is  titrated  until  a 
blue  color  of  short  duration  is  formed  (i  Sb2O3  =  4  I).  The  acids 
present  are  best  determined  after  precipitation  of  the  antimony 
with  hydrogen  sulphide.  Oxalic  acid  is  recognized  by  the  precipi- 
tate in  acetic  acid  solution  by  calcium  chloride. 

6.  Copper  Mordants. 

Blue  vitriol  is  principally  used,  and  sometimes  copper  acetate. 
The  copper  is  estimated  in  the  usual  manner.  Iron  should  be 
tested  for  qualitatively  and  its  quantity  estimated. 

B.  Tanning  Materials. 

Chemically,  tanning  substances  are  not  yet  sufficiently  understood 
to  allow  of  their  precipitation  in  isolated  conditions  or  in  the  form 
of  characteristic  compounds.  In  consequence,  the  customary 
methods  cannot  be  claimed  to  be  exactly  scientific. 


148  CHEMICAL-TECHNICAL    ANALYSIS. 

Practically  they  yield  approximate  satisfactory  results,  providing 
that  the  material  present  which  tans  is  designated  as  the  tanning  sub- 
stance ;  that  is,  those  organic  substances  which  are  absorbed  from 
their  solutions  by  the  hide.  Hereby  a  number  of  different  chem- 
ical substances  under  the  general  name  of  ' '  Tanning  Substance  ' ' 
are  usually  determined. 

Of  the  customary  methods,  the  procedure  of  Simand  and  Weiss, 
of  the  Vienna  Experimental  Station,  will  be  described.  This  has  re- 
cently become  popular.  According  to  these  chemists  a  portion  of 
the  solution  containing  tannin  is  evaporated  and  the  constituents 
soluble  in  hot  water  are  then  weighed.  In  another  portion  the 
non -tannins,  soluble  in  hot  water,  are  estimated  by  evaporating  the 
solution  from  which  the  tannins  have  been  withdrawn  by  hide 
powder.  The  remaining  substance  is  found  from  the  difference. 

1.  Tannin  Extracts. 

(#)  Water  and  ash.  2-3  grs.  extract  are  evaporated,  if  neces- 
sary, in  a  platinum  dish,  and  are  dried  to  constant  weight  at  100°. 
The  loss  of  weight  represents  water.  The  residue  is  ignited  and 
weighed  as  ash. 

(<£)  Matter  soluble  in  hot  water.  A  weighed  amount  of  the  ex- 
tract containing  at  least  10-12  grs.  of  the  dry  material  is  dissolved 
in  water,  placed  in  a  liter  flask,  and  upon  cooling  is  diluted  to  the 
mark  and  filtered.  100  c.c.  clear  filtrate  are  evaporated  in  a 
weighed  platinum  dish,  are  dried  to  constant  weight  at  100°,  and 
weighed.  The  residue  is  ignited,  the  ash  is  deducted,  and  the  dif- 
ference is  considered  as  soluble  organic  matter  (tanning  substances 
and  non -tanning  substances). 

(c}  Organic  matter  insoluble  in  hot  water.  If  the  percentages 
of  ash,  water  and  organic-  matter  soluble  in  water  found  as  in  (a) 
and  (<£)  are  deducted  from  100,  the  organic  matter  insoluble  m  hot 
water  is  obtained. 

(//)  Non-tannins.  A  tube  2—2.5  cm.  wide,  12  cm.  high,  not  too 
thin,  open  at  both  ends  and  possessing  rounded  edges,  is  closed  at 
the  lower  end  with  a  cork,  which  should  not  extend  too  far  into  the 
tube.  This  is  charged  with  6  grs.  hide  powder  in  such  a  way  as  to 
be  evenly  distributed  without  the  presence  of  any  marked  gaps  at 
the^  walls.  The  tube,  as  prepared,  which  should  still  possess  an 


RAW    PRODUCTS. 


149 


JftiMcr 


empty  space  3  cm.  high  above  the  powder,  is  placed  in  a  beaker 
13-14  cm.  high  and  5  cm.  wide.  The  beaker  is  gradually  filled 
with  the  solution  prepared  as  in  (£),  without  allowing  the  solution 
to  touch  the  powder  from  above.  After  a  few  hours  the  solution 
will  have  risen  from  below  in  the  inner  tube,  above  the  surface  of 
the  hide  powder.  By  means  of  a  tight-fitting  rubber  stopper,  con- 
taining one  perforation,  a  siphon  filled  with  water  (described  be- 
low) is  inserted  in  such  a  way  in  the  upper  part  of  the  tube  con- 
taining hide  powder  as  to  dip  into  the  liquid,  but  somewhat  above 
the  upper  surface  of  the  hide  powder.  The  liquid,  now  clear,  is 
gradually  drawn  off.  The  first  30  c.c.  liquid  are  discarded.  The 
following  100  c.c.  are  evaporated  and  dried  to  constant  weight. 
If  the  ash  be  deducted  from  the  resulting  residue,  the  difference 
gives  the  non-tanning  matter. 

The  siphon  previously  referred  to  is  a 
glass  tube  twice  bent  at  right  angles,  one 
arm  of  which  is  short  and  is  placed  in  the 
tube  containing  the  hide  powder,  whereas 
the  other  is  twice  the  length  of  the  tube 
containing  the  powder  and  extends  down- 
wards. The  horizontal  part  of  the  tube  is 
about  4  cm.  long. 

(e)  Tanning  substances.  They  are  deter- 
mined by  deducting  the  non-tanning  sub- 
stances (d)  from  the  matter  soluble  in  hot 
water  (<£). 

2.  Raw  Products. 

In  order  to  make  the  above  described 
methods  applicable  to  raw  products  used  in 
tanning  (barks,  wood,  etc.),  a  solution  con- 
taining i— 1.2  grs.  dry  material  in  100  c.c. 
is  prepared  by  exhausting  the  material  in 
question  with  water. 

For    extraction    the  following    apparatus   FIG.  12.— Extraction  Appara- 

,-,-,.  ,  ,    .          .        ,,.  ._  tus  for  Tanning  Materials. 

(rig.  12)  was  prepared  by  the  Vienna  Ex- 
perimental Station.     A  is  a  wide-mouth  flask  of  more  than  i  liter 
capacity.     In  this  the  mantle  B  is  inserted  through  a  hole  in  the 
stopper.     The  former  is  made  of  sheet  copper,  which  is  tin-plated. 


150  CHEMICAL-TECHNICAL    ANALYSIS. 

On  the  upper  end  a  low  copper  ring  C  is  joined,  and  in  the  trough 
so  formed  is  fitted  the  sheet  copper,  tin-plated,  cover,  D.  A  rub- 
ber ring,  Ey  set  in  the  trough,  and  two  diametrically  opposite 
bayonette  clasps,  serve  to  make  the  jacket  steam-tight  when  the 
cover  is  adjusted.  The  cover  is  closed  by  a  cork  stopper,  through 
which  a  fairly  wide  tube  issues  to  a  condenser.  Inside  the  cover 
a  tin  plate  is  soldered,  which  is  depressed  somewhat  toward  the 
center,  and  which  is  provided  with  pea-sized  perforations,  so  that 
the  condensed  water-drops  are  equally  distributed.  In  the  space 
formed  inside  of  the  jacket  and  lid  the  vessel  G  is  placed  as  a  re- 
ceptacle for  the  material.  This,  as  well  as  the  siphon,  issuing  from  an 
opening  in  the  bottom,  and  the  perforated  floor  Hy  is  made  of  tin. 

The  vessel  G  is  sufficiently  large  to  conveniently  hold  the  neces- 
sary quantity  of  material  to  be  extracted.  According  to  Eitner, 
Weiss  and  Anderen,  of  pine  and  oak  bark,  quebracho  wood,  etc. , 
50-60  grs.  should  be  extracted;  of  gall  nuts,  valonia,  etc.,  20-25 
grs.  should  be  extracted. 

A  similar  apparatus,  but  made  of  glass,  was  also  prepared  by  the 
Vienna  Station.  Both  forms  are  obtainable  from  Stefan  Baumann, 
Vienna,  VIII,  Florianigasse  n. 

The  examination  of  the  extract  so  obtained  is  conducted  in  ex- 
actly the  same  manner  as  that  described  under  tanning  extracts. 
The  objection  made  to  the  above  procedure  is  that  the  concentrated 
solutions  prepared  in  the  heat  precipitate  difficultly  soluble  tannin 
upon  cooling,  thereby  causing  loss.  A  method  based  on  a  similar 
principle,  in  which,  however,  much  more  dilute  solutions  are  used, 
has  been  perfected  by  v.  Schroeder.  As  far  as  we  know  the  Vienna 
method  is  at  present  the  most  popular,  and  among  other  countries  it 
is  practiced  in  England. 


X.  Textile  and  Dyeing  Industries. 


THIS  section  embraces  a  large  number  of  raw  materials  and  sub- 
stances used  technically,  which  may  be  arranged  in  the  following 
groups  :  Textile  fabrics,  bleaching  materials,  wool-oiling  material, 
thickening  material,  dressing  and  finishing  materials,  tanning  mate- 
rials, mordants  and  dyes.  Some  of  these  groups,  such  as  wool- 
oiling  material,  tannins  and  mordants,  have  already  been  treated  of 
in  previous  chapters. 

Others  are  brought  into  commerce  in  so  many  different  forms 
and  kinds  that  only  a  few  instances  will  have  to  suffice. 

1.  Textile  Fibers. 

The  best  means  of  distinguishing  the  textile  fibers  is  the  micro- 
scope, for  the  use  of  which  reference  only  will  be  made  to  the  ex- 
cellent little  work  of  v.  Hohnel.*  The  chemical  points  of  differ- 
ence between  animal  and  vegetable  fibers  are  : 

(a)  Behavior  when  burned.  When  animal  fibers  are  burned 
they  disseminate  the  peculiar  odor  of  burning  nitrogenous  matter. 
They  burn  much  slower  than  vegetable  fiber. 

The  former  leave  a  voluminous,  difficultly  combustible  coke,  and 
the  latter  incinerate  easily  and  completely. 

(/3)  Behavior  toward  alkalies.  Boiling  with  a  10  per  cent,  solu- 
tion of  potassium  or  sodium  hydrate  dissolves  animal  fibers,  whereas 
vegetable  fibers  remain  practically  unattacked. 

(y)  Behavior  toward  acid.  After  treatment  for  2—3  hours  with 
dilute  acid,  especially  sulphuric  acid  (sp.  gr.  1.03-1.04),  and  sub- 
sequent drying  at  about  100°,  vegetable  fibers  are  destroyed  (carbon- 
ized), while  animal  fibers  are  scarcely  attacked. 

Chloride  of  magnesium  and  chloride  of  aluminium  solutions 
which  give  off  acid  above  100°  react  similarly. 

*  Die  Microscopic  der  technisch  verwendeten  Faserstoffe  von  F.  v.  Hohnel, 
Wien,  1887. 


152  CHEMICAL-TECHNICAL    ANALYSIS. 

(d)  Behavior  toward  nitrating  mixture.  According  to  Peltier, 
the  fibers  under  examination  are  immersed  for  about  ^  hour  in  a 
mixture  of  equal  volumes  cone,  sulphuric  acid  and  cone,  nitric  acid, 
after  which  they  are  washed  with  much  water.  Silk  is  thereby 
completely  dissolved,  wool  is  colored  yellow  or  light  brown, 
whereas  vegetable  fibers  change  neither  in  color  nor  structure,  but 
yield  highly  combustible  gun-cotton  when  dried. 

(a)  Half- "Woolen  Yarns  and  Fabrics. 

Moisture,  fat  and  cotton  are  determined  in  these,  and  the  wool  is 
obtained  by  difference. 

(a)  Moisture.  About  10  grs.,  if  necessary,  more,  are  dried  at 
100°  to  constant  weight. 

(/2)  Fat.  The  sample  dried  according  to  (a)  is  extracted  in  a  suit- 
able apparatus  with  ether.  The  ethereal  solution, filtered,  if  necessary, 
is  placed  in  a  weighed  flask,  the  ether  is  distilled  off,  and  the  last 
traces  are  removed  by  a  current  of  air  until  a  nearly  constant 
weight  is  obtained.  The  fat  so  obtained  may,  if  necessary,  be 
tested  for  saponifiable  and  unsaponifiable  constituents.  Soaps,  if 
present,  do  not  dissolve  in  the  ether.  They  may  be  determined  by 
extraction  with  alcohol  subsequent  to  the  extraction  with  ether. 

(>)  Cotton.  The  dried  sample,  freed  from  fat,  is  placed  in  a 
boiling-hot  10  per  cent,  solution  of  caustic  potash;  the  boiling  is 
continued  for  15  minutes,  when  the  whole  is  poured  into  a 
beaker  filled  with  distilled  water.  The  remaining  cotton  is  re- 
moved, wrung  out,  well  washed,  and  finally  dried  at  100°  to  con- 
stant weight. 

(<J)  Sheep's  wool  is  estimated  by  the  difference  reckoned  on  100. 

(b)  Half-Silk. 

In  fabrics  containing  silk  and  cotton,  the  cotton  can  be  estimated 
by  the  method  described  under  (a,  y). 

(c)  Shoddy. 

This  consists  of  a  mixture  of  unused  wool  fibers  and  more  or 
less  already  used  fibers,  which  sometimes  contain  cotton. 

To  determine  the  animal  fibers,  shoddy,  like  half- wool,  is  subjected 
to  the  alkali  treatment.  Microscopically,  shoddy  can  be  detected 
by  the  fact  that,  while  in  the  main  it  consists  of  uniformly  col- 


BLEACHING    MATERIALS.  153 

ored  fibers,  other  differently  colored  fibers  are  present,  which 
shows  that  a  uniform  dyeing  process  was  not  used.  Besides  this, 
innumerable  gaps,  as  well  as  wool  fibers  of  very  different  charac- 
ter, can  usually  be  detected  in  shoddy.  A  separation  of  the  differ- 
ent fibers  present,  and  these,  with  an  approximate  idea  of  the  rela- 
tion of  one  to  the  other,  can  also  be  conducted  with  the  micro- 
scope, but  requires  considerable  practice.* 

(d)  Oxycellulose. 

This  is  formed  by  the  action  of  many  oxydizing  agents,  such  as 
chlorine,  bleaching  lime,  hydrogen  peroxide,  potassium  perman- 
ganate, and  chromic  acid  on  cotton,  and  can,  therefore,  frequently 
arise  in  the  bleaching  process.  Its  production  must  be  carefully 
avoided  on  account  of  the  consequent  weakening  of  the  cotton 
fiber,  which  becomes  especially  evident  in  the  subsequent  treatment 
with  alkalies,  soda  or  soap. 

The  property  of  oxycellulose  of  absorbing  basic  dye  can  be  made 
use  of  as  a  test,  according  to  Witz.  The  cotton  to  be  tested  is 
placed  in  a  ^  per  cent,  solution  of  methylene  blue.  Those  por- 
tions which  are  changed  to  oxycellulose  are  colored  more  or  less 
blue.  Better  than  this  method  is  the  power  of  oxycellulose  to  re- 
duce Fehling's  solution.  For  this  purpose,  the  fabric,f  which  is 
prepared  by  repeated  boiling  with  water,  or,  better,  by  digesting 
with  malt  infusion  at  65°,  is  boiled  for  5  minutes,  stirring  con- 
stantly with  a  mixture  of  equal  parts  Fehling's  solution,  to  which 
an  equal  volume  of  water  has  been  added.  Thereupon  the  fabric 
is  washed.  Those  parts  containing  oxycellulose  are  recognized  by 
the  rose  color  which  arises  from  deposited  cuprous  oxide.  This  be- 
comes more  intense  the  more  oxycellulose  is  present  in  the  fabric. 

The  yellow  color  produced  on  oxycellulose  spots  by  warming  the 
fabric  with  alkaline  /3-naphthol  solution  can  be  used  as  a  test.  How- 
ever, this  reaction  is  less  sensitive. 

2.  Bleaching-  Materials. 

Sulphurous  acid, sodium  bisulphite  and  hydrogen  peroxide  are  prin- 
cipally used  to  bleach  animal  fibers.  Beside  these,  chloride  of  lime 

*  See  Dr.  F.  R.  v.  Hohnel.  Die  Microscopic  der  technisch  verwendeten 
Faserstoffe,  Wien. 

f  Starch  especially  is  often  difficult  to  remove. 


154  CHEMICAL-TECHNICAL    ANALYSIS. 

is  used  in  bleaching  vegetable  fibers.  It  is  taken  for  granted  that 
the  examination  of  all  these  substances  is  known.*  Recently  salts 
of  persulphuric  acid  (persulphates)  have  been  used  as  bleaching 
agents.  The  bleaching  action  depends  on  their  strongly  oxidizing 
properties.  The  following  reaction  of  decomposition  of  the  am- 
monium salts  demonstrates  this  : 

(NH4)2S208+H20  =  (NH4)2S04+H2S04+0. 

The  estimation  of  the  active  oxygen,  according  to  Ulzer,  is  con- 
ducted as  follows :  f 

About  .3  gr.  sample  is  decomposed  by  addition  of  an  excess 
of  ferrous  ammonium  sulphate  solution  (1—1.5  grs-)  and  dilute  sul- 
phuric acid.  The  solution  is  boiled  for  y>,  hour  in  a  current  of 
carbonic  acid  or  in  a  flask  provided  with  a  Bunsen  valve,  and  the 
excess  of  ferrous  salt  is  titrated  back  with  permanganate.  From 
the  ferrous  ammonium  sulphate  oxidized,  the  active  oxygen  can  be 
calculated,  and  from  this,  by  the  above  equation,  the  persulphate 
is  found. 

Ammonium  persulphate  is  the  common  form. 

3.  Sizing  Materials. 

These  serve  on  the  one  hand  for  the  preparation  of  dressings,  on 
the  other  hand  for  the  laying  on  of  coloring  matter  in  calico  print- 
ing. The  different  kinds  of  starch  and  flour,  dextrin,  gums,  traga- 
canth,  albumin,  casein,  and  many  others,  are  used.  The  investiga- 
tion of  these  products  is  often  difficult  and  uncertain.  Starch, 
dextrin  and  a  few  reactions  for  gums  only  will  be  described. 

(a)  Starch. 

The  chemical  examination  of  starch  has  already  been  described 
in  Chapter  VI.  Microscopic  means  are  employed  to  distinguish 
between  the  different  varieties. 

(b)  Dextrin. 

Dextrin  is  obtained  by  the  action  of  dilute  acids  on  starch  at 
high  temperature,  also  by  heating  per  se ;  and  it  contains,  in  addi- 
tion, water,  ash,  maltose,  starch,  and  other  organic  substances. 
The  determinations  of  these  constituents,  as  well  as  the  acidity,  are 
conducted  according  to  Hanofsky  as  follows  : 

*  Contribution  from  the  K.  K.  tech.  Gewerbe- Museum,  Jhrg.  1895,  p.  310. 
f  See  Appendix. 


SIZING    MATERIALS.  155 

25  grs.  dextrin  are  placed  in  a  flask  of  500  c.c.  capacity  and  are 
well  shaken  with  cold  water,  filled  to  the  mark,  allowed  to  settle, 
and  are  filtered  through  a  ribbed  filter.  In  the  filtrate,  maltose, 
dextrin  and  acidity  are  determined. 

(«)  Maltose.  This  is  determined  by  the  cuprous  oxide,  which 
it  has  the  power  to  precipitate  from  Fehling's  solution. 

Since  the  power  of  reduction  changes  with  the  concentration,  the 
latter  must  be  made  the  same  always.  A  test  is  made,  therefore 
(similar  to  that  of  invert  sugar,  p.  85,),  to  determine  how  much 
of  the  solution  is  required  to  reduce  10  c.c.  Fehling's  solution. 
In  the  actual  determination  1—2  c.c.  less  are  taken,  and  are  diluted 
with  sufficient  water  to  bring  the  total  volume  to  57—58  c.c.  The 
liquid  is  run  into  a  porcelain  dish  in  which  10  c.c.  Fehling's  solu- 
tion have  previously  been  placed.  It  is  heated  to  boiling,  and  is 
kept  in  that  state  exactly  4  minutes.  The  precipitated  cuprous 
oxide  is  thrown  on  the  asbestos  filter,  and  is  treated  further  in  the 
usual  manner.  Using  the  concentration  referred  to,  113  copper  — 
100  anhydrous  maltose,  the  percentage  of  maltose  so  found  =  M. 

(/?)  Dextrin.  50  c.c.  solution  are  diluted  to  200  c.c.,  and  are 
heated  to  incipient  boiling  on  a  reflux  with  15  c.c.  hydrochloric 
acid  (sp.  gr.  1.125)  for  two  hours.  Dextrin  and  maltose  are 
thereby  changed  to  dextrose,  the  solution  is  filtered  into  a  500 
c.c.  flask,  is  nearly  neutralized  with  caustic  soda,  and  diluted  to  the 
mark.  The  dextrose  in  25  c.c.  is  determined  with  Fehling's  solu- 
tion. If  the  dextrose  in  per  cent.  =  D,  the  dextrin  will  be 

.9  (D-i.05  M), 
since  20  parts  dextrose  correspond  to  19  parts  maltose. 

(7)  Acidity.  50  c.c.  solution  are  titrated  with  one-tenth  nor- 
mal alkali,  using  phenol-phthalein  as  indicator.  The  quantity  of 
one-tenth  normal  alkali  calculated  in  100  grs.  substance  is  desig- 
nated the  acidity. 

(fl)  Starch.  2.5-3  grs-  dextrin  are  mixed  with  200  c.c.  water 
and  are  treated  with  15  c.c.  hydrochloric  acid  (sp.  gr.  1.125),  as 
in  (/3).  The  solution  is  nearly  neutralized,  diluted  to  500  c.c., 
and  likewise  treated  for  the  dextrose  in  25  c.c.  Maltose,  dextrin 
and  starch  are  converted  into  dextrose.  If  the  percentage  of  dex- 
trose =  D,  then  the  percentage  of  starch  will  be 

•9  (D-D)- 


156  'CHEMICAL-TECHNICAL   ANALYSIS. 

(77)  Water  and  ash  are  determined  in  the  usual  manner.  If  the 
water  =  W  per  cent,  and  the  ash  A  per  cent.,  the  "  other  organic 
constituents  ' '  present  will  be 

TOO— (Mdtose+Dextrin+Starch-fW  +  A). 

(c)  Gums. 

Of  the  many  kinds  of  gums,  gum  arabic,  gum  Senegal  and  gum 
tragacanth  are  chiefly  used. 

These  three  varieties  can  be  distinguished  in  pure  condition  by 
their  appearance.  Gum  arabic  is  more  easily,  gum  Senegal  less 
readily  soluble  in  water,  whereas  gum  tragacanth  is  scarcely  soluble 
at  all,  but  swells  up  to  a  slimy  mass,  which  distributes  itself  through- 
out a  sufficient  quantity  of  water.  Gums  are  frequently  adulterated 
with  dextrin. 

Lieberman  has  proposed  the  following  tests  for  the  detection  of 
gum  Senegal  and  dextrin  in  gum  arabic.  The  gum  is  dissolved  in 
hot  water,  treated  with  an  excess  of  caustic  potash  and  some 
copper  sulphate,  slightly  warmed  and  filtered.  The  milky  filtrate 
is  boiled.  A  perceptible  precipitate  of  cuprous  oxide  indicates  the 
presence  of  dextrin. 

The  precipitate  formed  by  the  action  of  caustic  potash  in  the 
copper  sulphate,  and  which  contains  the  gum  acids,  is  washed  with 
water,  dissolved  in  dilute  hydrochloric  acid,  and  precipitated  with 
alcohol.  It  is  allowed  to  settle  for  %-i  day,  when  the  supernatant 
liquid  is  poured  off.  The  precipitated  gum  in  the  vessel  is  washed 
with  alcohol,  dissolved  in  hot  water,  and  to  it  are  added  an  excess 
of  caustic  potash  and  some  copper  sulphate.  A  balled-together 
precipitate,  quickly  ascending  to  the  surface,  indicates  gum  arabic, 
whereas  a  more  divided,  fine  flocculent  precipitate  discloses  gum 
Senegal  or  an  admixture  of  the  same.  In  the  first  instance,  in  ad- 
dition, an  aqueous  solution,  boiled  with  caustic  potash,  should  turn 
amber  yellow.  If  the  amber  color  arise  in  the  second  case  under 
the  same  conditions  a  mixture  of  Senegal  gum  and  gum  arabic  is 
present,  whereas  a  faint  yellow  or  no  color  indicates  Senegal  gum 
alone. 

4.  Finishing  Materials. 

The  number  of  substances  used  for  dressings  is  very  large  and  is 
on  the  increase.  In  consequence  only  the  most  important  will  be 


FINISHING    MATERIALS.  157 

selected,  and  the  part  which  they  play  in  finishing  will  be  men- 
tioned. 

(«)  Sizing  material.  These  were  treated  of  in  the  previous 
chapter. 

(/3)  Substances  which  make  the  goods  soft,  pliable  and  hygro- 
scopic :  Glycerin,  grape  sugar,  fats,  tallow,  stearin,  paraffin,  cocoa- 
nut  oil,  wax,  ozokerite,  calcium  chloride,  zinc  chloride,  sodium 
and  ammonium  salts. 

(y)  Loading  materials.  Gypsum,  chalk,  barium  sulphate  (per- 
manent white),  sulphate  of  magnesium,  sodium  and  zinc,  talc, 
china  clay,  magnesium  chloride,  barium  chloride,  barium  carbon- 
ate, lead  sulphate. 

(<S)  Coloring  matters.  Ultramarine  blue,  Berlin  blue,  indigo 
blue,  indigo  carmine,  all  kinds  of  blue  cotton-dyes,  ammoniacal 
cochineal,  black,  gray  and  brown  mineral  pigments. 

(>?)  Antiseptics.  Phenol,  creosote,  salicylic  acid,  tannin,  cam- 
phor, oxalic  acid,  zinc  salts,  boracic  acid,  borax,  alums,  aluminium 
sulphate,  formic  acid,  etc. 

(e)  Water-proof  materials.  Fats,  varnishes,  resins,  paraffin, 
tannin,  basic  aluminium  acetate  and  aluminium  soaps.  Besides 
these  there  may  be  contained  materials  which  render  the  fabric  fire- 
proof, such  as  boric  acid,  phosphates,  silicates,  etc.,  and  such  as 
impart  metallic  lustre  to  the  goods :  metallic  sulphides,  metal- 
dust,  etc. 

With  this  array  of  substances  no  general  method  of  investigation 
of  finishing  materials  can  be  given. 

In  the  following,  the  analysis  of  two  simple,  frequently  occurring 
products  are  described : 

(0)  Finishing  material  containing  starch  paste  and  chloride  of 
magnesium. 

(a)  Starch.  10—20  grs.  material  are  heated  for  three  hours  to 
incipient  boiling  in  a  500  c.c.  flask  with  200  c.c.  water  and  20  c.c. 
hydrochloric  acid  (sp.  gr.  1.125).  To  avoid  evaporation  of  the 
water  a  reflux  is  used.  Upon  cooling,  the  contents  are  poured  into 
a  500  c.c.  measuring-flask,  and  an  excess  of  caustic  soda  is  added 
to  precipitate  all  the  magnesia  capable  of  precipitation  by  alkali. 
The  solution  is  filled  to  the  mark  and  is  rapidly  filtered  through  a 
dry  filter.  In  25  c.c.  filtrate  the  dextrose  formed  by  inversion  is 


158  CHEMICAL-TECHNICAL    ANALYSIS. 

estimated  by  means  of  Fehling's  solution,  as  is  described  under 
starch  (p.  99). 

(/?)  Magnesia  and  chlorine.  The  determination  of  these  constit- 
uents in  the  ash  is  not  possible  on  account  of  the  easy  decomposi- 
tion of  magnesium  chloride.  The  presence  of  starch  likewise  in- 
terferes with  the  precipitation.  The  latter  is  therefore  inverted 
with  dilute  nitric  acid  as  in  (a)  and  in  one  portion  the  chlorine,  and 
in  another  portion  the  magnesa  are  determined  by  the  usual  methods. 

O)  Water  and  ash.  An  exact  determination  of  these  constitu- 
ents cannot  be  accomplished  on  account  of  the  easy  decomposition 
of  magnesium  chloride  and  the  tenacity  with  which  water  adheres. 
Nevertheless,  approximate  results  can  be  obtained  by  drying  a 
weighed  portion  at  about  100°  to  almost  constant  weight  and  in- 
cinerating the  residue.  The  water  of  crystallization  of  magnesium 
chloride  is  for  the  greater  part  still  present  after  drying. 

(£)  Finishing  material,  containing  starch  paste,  fat  and  sulphate  of 
zinc. 

(«)  Starch,  zinc  oxide  and  sulphuric  acid.  10—20  grs.  material 
are  inverted  as  before  with  hydrochloric  acid,  separated  from  the 
fat  by  nitration  through  a  moistened  filter,  and  diluted  to  500  c.c., 
after  approximate  neutralization  with  caustic  soda.  The  starch  is 
determined  as  before  in  25  c.c.  of  this  solution.  Other  measured 
portions  are  used  for  the  determinations  of  zinc  oxide  and  sulphuric 
acid  by  the  usual  methods. 

(£)  Fat.  Since  the  fat  separated  in  (a)  does  not  usually  answer 
for  further  examination,  a  larger  portion  of  the  finishing  material 
is  preferably  taken.  It  is  inverted  with  hydrochloric  acid,  and  the 
separated  fat  is  extracted  repeatedly  by  shaking  with  ether.  The 
collected  ethereal  extractions  are  freed  from  ether  by  distillation  and 
the  last  portions  of  the  solvent  are  removed  by  a  current  of  air, 
after  which  the  residue  is  weighed.  It  contains  the  total  fat.  In 
the  latter,  the  usual  constants,  such  as  saponification  number,  iodine 
number,  etc. ,  can  be  determined  in  addition  to  unsaponifiable  por- 
tions of  the  fat.  The  nature  of  the  latter  is  thus  ascertained. 

5.  I>ye-Stuffs. 

These  are  divided  into  natural  and  artificial  dye  stuffs,  according 
to  their  origin.  According  to  their  use,  they  may  be  divided  into 
basic,  acid,  mordant  and  direct  cotton  dye-stuffs. 


DYE-STUFFS.  159 

To  these  are  added  a  number  of  dye-stuffs  formed  directly  on  the 
fiber,  such  as  "vat"  dyes,  diazotized  dyes  and  aniline  black. 
Each  of  these  groups  represents  a  special  dyeing  process,  which 
will  be  briefly  discussed  here. 

Basic  dyes,  applied  to  cotton. — The  material  to  be  dyed  must  first 
be  mordanted.  Mordanting  is  usually  conducted  in  the  following 
manner  :  The  cotton  is  first  placed  in  a  bath  of  tannin  at  60°  for 
about  12  hours,  after  which  it  is  thoroughly  wrung  out  and  placed 
in  a  bath  of  tartar  emetic,  10-20  grs.  per  liter,  or  the  correspond- 
ing amount  of  antimony  salt  [SbFl3.  (NH4).2SO4].  Thereupon  it  is 
washed  well  and  dyed  in  the  bath  containing  the  dye  at  a  tempera- 
ture of  50—60°  until  the  bath  is  exhausted. 

Applied  to  wool. — Takes  place  in  a  bath  which  is  either  neutral 
or  slightly  acidified  with  acetic  acid.  The  bath  is  gradually  heated 
to  boiling. 

Applied  to  silk. — Takes  place  in  neutral,  slightly  acid  (acetic) 
or  separate  soap  bath,  with  gradually  heating  to  about  70°. 

Among  the  basic  dyes  belong  fuchsin,  auramin,  malachite  green, 
victoria  blue,  methyl  violet,  etc. 

Acid  dyes  find  use  chiefly  in  dyeing  wool.  Dyeing  is  conducted  in 
a  bath  containing  2—4  per  cent,  sulphuric  acid,  or  2-5  per  cent, 
sulphuric  acid  and  10-15  Per  cent.  Glauber  salt,  or  5-10  per  cent, 
sodium  bisulphate.  A  gradual  rise  in  temperature  and  eventually 
continuous  boiling  are  required. 

The  group  of  basic  dyes  is  very  extended.  There  may  be  men- 
tioned, for  instance :  Ponceau,  naphthol  black,  alkali  blue,  patent 
blue,  acid  fuchsin,  acid  violet. 

Mordant  dye-stuffs. — The  dyeing  of  cotton  as  well  as  of  wool  re- 
quires previous  mordanting.  Aluminium,  chromium  and  iron  mor- 
dants are  chiefly  used.  Mordanting  wool  is  accomplished  by  boil- 
ing 1-2  hours  in  the  solution  of  the  mordant  (3-4  per  cent,  potas- 
sium bichromate,  6— 10  per  cent,  aluminium  sulphate,  4-6  per  cent, 
ferrous  sulphate)  with  the  addition  of  sulphuric  acid  (i  per  cent.), 
acid  potassium  tartrate  (3-8  per  cent.),  or  oxalic  acid  (1-2  per 
cent).* 

Cotton  mordanting  must  be  accomplished  by  an  artificial  fixation 

*  Recently  lactic  acid  has  also  found  use. 


160  CHEMICAL-TECHNICAL    ANALYSIS. 

with  chemical  precipitants.  The  cotton  is  first  placed  in  a  fairly 
strong  solution  of  the  mordant  (aluminium  sulphate,  aluminium 
acetate,  chrome  alum,  chromium  fluoride,  ferric  nitrate).  It  is  then 
pressed  out  and  passed  through  a  bath  containing  soda,  chalk,  am- 
monium carbonate,  etc.  Finally  it  is  well  washed. 

Iron  and  tin  baths  are  used  mostly  for  silk.  As  a  rule,  a  simulta- 
neous ''weighting"  occurs,  and  sometimes  also  the  silk  becomes 
colored,  as,  for  instance,  with  acetate  of  iron  and  tannin.  In  such 
cases  the  operation  must  be  repeated  several  times. 

Dyeing  mordanted  goods  is  conducted  in  neutral  baths.  On  ac- 
count of  the  insolubility  of  many  mordant  dyes,  the  bath  must  be 
kept  in  motion  during  the  process  of  dyeing.  Also,  in  order  to 
insure  uniform  dyeing,  the  temperature  must  increase  very  slowly. 
To  the  mordant  dyes  belong  the  large  group  of  alizarin  dyes  and 
most  of  the  natural  dye-stuffs,  blue  wood,  yellow  wood,  red  wood, 
cochineal,  etc. 

Direct  cotton  dye-stuffs.  (Benzidine  colors  also  dye  vegetable 
fibers  directly.)  Dyeing  is  usually  conducted  in  weak  alkaline 
baths  (soda,  soap,  2-5  percent.;  borax,  sodium  aluminate,  5-10  per 
cent. ,  and  sometimes  in  neutral,  salt,  Glauber  salt,  or  weakly  acid 
baths).  The  operation  usually  takes  place  at  a  boiling  tempera- 
ture. This  group  is  also  very  large.  To  it  belong,  among  others, 
benzopurpurin,  chrysamin,  benzoazurin,  diamine  blue,  diamine 
black. 

"Vat"  dyeing  is  almost  exclusively  conducted  with  indigo.* 
The  insoluble  indigo  blue  or  indigotin  contained  therein  must 
first  be  transformed  in  the  vat  into  soluble  indigo  white.  Reducing 
agents  mostly  used  are  ferrous  sulphate  (iron  vat),  zinc  dust  (zinc 
vat),  hyposulphurous  acid  (hydrosulphite  vat).  The  fabric  im- 
pregnated with  indigo  white  is  rapidly  colored  blue  by  oxidation 
in  the  air. 

Diazotized  dyes. — Benzidine  dye-stuffs  can  be  diazotized  in  the 
fiber  and  developed  in  a  bath  containing  dissolved  phenols,  naph- 
thols  or  amines.  A  new  color  is  formed  which  is  similar  to  the 
original,  but  more  perfect,  and  which  is  distinguished  for  its  fast- 
ness. The  developers  mostly  used  are  phenol,  resorcin,  /S-naphthol, 

*  Recently  the  artificially  prepared  indophenol  has  come  into  use. 


DYE-STUFFS.  161 

m.  phenylenediamine,  naphthylamine  ethers,  amido  diphenylamine, 
and  others.  The  colors  produced  are  also  called  ingrain  or  devel- 
oped colors.  As  an  example,  the  diazotizing  of  primuline,  first 
attempted,  may  be  mentioned.  The  goods  are  dyed  as  usual  at 
first.  They  are  then  washed  and  placed  in  a  diazotizing  bath  con- 
taining in  200  parts  water  i  part  sodium  nitrite  and  the  requisite 
quantity  of  sulphuric  or  hydrochloric  acid  (sulphuric  acid,  about 
twice  as  much,  and  hydrochloric  acid,  about  three  times  as  much 
as  the  quantity  of  sodium  nitrite).  The  diazotizing  bath  is  kept  cool 
by  addition  of  ice.  After  short  immersion,  the  goods  are  rinsed  in 
cold  water  and  are  placed  in  the  developing  bath.  This  may  con- 
sist of  an  alkaline  solution  of  phenol,  resorcin,  /3-naphthol,  a  solution 
of  m.  phenylaminediamine  hydrochloride,  etc.  The  developing 
bath  is  usually  kept  cold.  The  goods  are  subsequently  rinsed. 

Somewhat  different  from  this  is  the  production  of  insoluble  azo 
dye-stuffs  on  fiber  which  has  not  been  previously  dyed. 

The  colors  so  produced  are  termed  "  ice  colors."  They  are  pre- 
pared for  dyeing,  especially  for  the  printing,  of  cotton  goods. 
The  goods  to  be  dyed  are  first  impregnated  with  an  alkaline 
solution  of  a-naphthol,  and  are  then  drawn  through  a  diazo  solu- 
tion. In  this  manner  there  is  produced  in  the  filter  an  azo  dye- 
stuff  which  is  quite  fast  toward  water  and  very  fast  toward  acid 
and  alkali.  As  an  example,  the  production  of  the  very  beautiful 
paranitraniline  red  may  be  mentioned.  144  grs.  ,9-naphthol  are  dis- 
solved in  10  liters  water,  and  145  grs.  caustic  soda  (sp.  gr.  1.333), 
with  addition  of  500  grs.  turkey-red  oil.  The  goods  are  impreg- 
nated with  this  solution  and  dried.  They  are  afterwards  placed  in 
the  diazotizing  bath.  The  latter  is  obtained  by  dissolving  in  a 
boiling  solution  of  69  grs.  paranitraniline  in  200  c.c.  hydrochloric 
acid  and  200  c.c.  water.  To  the  cooled  solution  i  liter  cold 
water,  and,  after  thorough  cooling,  500  grs.  ice  are  added.  It  is 
then  diazotized  with  250  c.c.  twice  normal  nitrite  solution,  is  di- 
luted to  10  liters  and  treated  with  300  grs.  sodium  acetate  before 
using.  The  goods,  which  are  removed  from  the  diazotizing  bath, 
are  well  rinsed,  slightly  soaped  at  40°,  and  dried. 

Aniline  black  is  a  dye-stuff  which  is  formed  on  the  fiber  by  the 
oxidation  of  aniline.  Potassium  bichromate  or  chlorate  are  usually 
used  as  oxidizers.  It  can  be  produced  on  cotton,  wool  or  silk. 

11 


162  CHEMICAL-TECHNICAL   ANALYSIS. 

Method  of  Testing. 

The  best  means  of  determining  the  value  and  strength  of  a  dye- 
stuff  is  by  comparative  dye  tests.  To  this  end  a  "  type  "  or  stand- 
ard sample  may  be  employed  for  comparison  ;  or,  when  a  choice  is  to 
be  made  between  several  kinds  of  the  same  dye,  the  process  may  be 
undertaken  with  all  the  samples.  In  the  first  case  dyeing  is  con- 
ducted under  the  same  condition  until  the  same  shade  is  obtained, 
and  a  comparison  is  made  between  the  amounts  of  dye  used.  They 
are  merely  proportional  to  the  value  of  the  dye-stuff.  In  the  second 
case  dyeing  is  conducted  with  dyes  in  quantity  of  equal  price  and 
the  colors  produced  are  compared.  A  process  of  dyeing  is  selected 
which  is  as  simple  as  possible,  and  which  gives  reliable  value  for  the 
strength  of  the  dye  and  the  clearness  of  the  shade.  In  order,  for 
instance,  to  avoid  mordanting  the  cotton,  wool  may  be  used  with 
basic  dyes.  The  quantity  of  mordant  is  rather  taken  somewhat 
higher  than  required  in  actual  practice  when  mordant  dyes  are  used. 
Wool  is  mordanted  in  the  manner  previously  mentioned.  Strips  of 
cotton  calico*  printed  with  iron  and  aluminium  mordants  are  prefer- 
ably used  instead  of  cotton.  The  quality  of  dye  chosen  should 
not  be  too  large,  because  lighter  shades  are  more  easily  compared. 
In  case  the  bath  is  not  exhausted,  a  second,  and,  if  necessary,  a  third 
sample  is  placed  in  the  same,  until  exhaustion  is  complete. 

The  samples  to  be  dyed  should  possess  equal  weight,  and  for 
carded  wool,  cotton  yarns  or  calico,  should  equal  about  10  grs.  If 
necessary,  they  are  first  mordanted  and  dyed  in  porcelain  or  glass 
vessels.  In  order  to  preserve  uniform  heat,  the  vessel  is  placed  in 
an  oil-  or  glycerin -bath.  The  quantity  of  water  used  is  about  50 
times  the  weight  of  the  goods  when  these  are  wool,  and  30  times  the 
weight  when  cotton  is  used.  The  evaporated  water  is  replaced  from 
time  to  time.  To  prepare  the  dye-stuff  solution,  i  gr.  per  liter  of 
coal-tar  colors  is  used,  and  10-20  grs.  dye-wood  extracts  per  liter. 
10-20  grs.  insoluble  dye-pastes  are  weighed  off,  mixed  with  one 
liter  water,  and  thoroughly  shaken  before  using.  The  dye-stuff  solu- 
tion is  added  from  a  burette  or  pipette  and  manipulated  as  pre- 
viously stated.  After  dyeing,  the  goods  are  washed,  and,  if  neces- 
sary, soaped.  If,  for  example,  in  one  case  70  c.c.,  in  another 

*  These  may  be  readily  purchased. 


DYE-STUFFS. 


163 


56  c.c.  of  two  solutions  containing  blue  wood  extract  (in  both  cases 
TO  grs.  extract  per  liter)  were  used,  their  value  will  be  the  reverse  : 
56  :  70  or  80  :  100. 

Tests  for  impurities. — Inorganic  admixtures  are  easily  recognized 
by  the  increased  ash.  The  nature  of  these  is  determined  in  the 
examination  of  the  latter.  Organic  impurities,  such  as  starch  and 
dextrin,  remain  behind  on  extraction  with  alcohol  in  many  cases, 
and  can  thus  be  determined  quantitatively. 


FIG.  13. — Indigo  Extraction  Apparatus. 

Special  Methods  of  Investigation. 

Special  methods  of  investigation  are  also  applied,  in  addition  to 
the  dye  tests,  to  certain  natural  dye-stuffs.  Of  these  the  examina- 
tion of  indigo  for  indigotin,  according  to  Schneider,  will  be  men- 
tioned. This  depends  on  the  solubility  of  indigotin  in  naphthalene. 
30-50  grs.  pure  naphthalene,  which  has  been  previously  melted  to 
expel  water,  are  placed  in  the  Erlenmeyer  flask,  K,  of  the  accom- 
panying apparatus  (Fig.  13).  The  Erlenmeyer  flask  may  be  re- 
placed by  a  wide-necked  test-tube. 


164  CHEMICAL-TECHNICAL    ANALYSIS. 

Thereupon  about  .3  gr.  of  air-dried  indigo  is  placed  in  the  ex- 
traction capsule  H  (these  are  for  sale  by  Schleicher  and  Schull), 
mixed  with  ignited  bar-sand  by  means  of  a  spatula,  or  by  shaking, 
and  covered  with  a  small  paper  plate.  It  is  then  hung  in  the  flask 
by  two  wires  which  are  inserted  into  the  sides  of  the  capsule.  The 
wires  are  pressed  against  the  inner  walls  by  the  cork  *$*.  Through 
a  hole  in  the  latter  there  is  placed  a  condenser-tube  R,  provided 
with  a  slanting  end  extending  into  the  capsule,  and  which  may 
have  an  opening  at  a  in  order  to  facilitate  the  issue  of  the  naph- 
thalene vapors.  This  is  not  indispensable,  however.  The  naph- 
thalene is  now  gradually  brought  to  boiling,  when  the  vapors, 
which  are  condensed  in  the  tube,  drop  into  the  capsule  and  extract 
the  indigotin.*  Any  solidified  naphthalene  in  the  tube  may  be  re- 
moved by  heating.  Heat  is  applied  until  the  naphthalene  which 
flows  from  the  capsule  remains  nearly  colorless  for  a  time.  It 
is  then  allowed  to  cool,  the  contents  of  the  flask  are  covered  with 
ether,  and  after  all  soluble  matter  has  gone  into  solution  the  residue 
is  thrown  on  a  dried  and  weighed  filter,  is  well  washed  with  ether, 
dried  at  100°  and  weighed  as  indigotin.  In  a  separate  portion  of 
the  sample  the  water  is  determined  by  drying  at  100°,  and  the  ash 
is  determined  by  first  subliming  off  the  indigotin  with  a  small 
flame  and  afterwards  igniting  briskly  to  constant  weight. 

Becognition  of  Dye-stuffs. 

The  behavior  of  the  dye-stuff  with  acids,  alkalies  and  reducing 
agents  serves  as  a  means  of  identification.  The  reactions  bearing 
on  this,  most  of  which  depend  on  changes  of  color  and  decolor- 
ization,  and  which  can  also  be  used  to  identify  a  dye  on  the  fiber, 
are  specially  treated  of  in  the  excellent  work  of  G.  Schultze  and 
P.  Julius,  i.e.,  "  Tabellarische  Uebersicht  der  kiinstlichen  organ  - 
ischen  Farbstoffe. ' '  A  detailed  description  at  this  point  would  be 
too  extensive. 

*  Indigo  red  is  also  extracted  by  naphthalene,  but  on  subsequent  treatment  with 
ether  it  dissolves,  while  indigo-blue  remains  undissolved. 


XI,  Products  of  the  Coal-Tar  Industry. 


I.  Crude  Benzene. 

(0)   DETERMINATION  of  petroleum  hydrocarbons. 

100  grs.  crude  benzene  are  nitrated  with  a  mixture  of  150  grs. 
nitric  acid  (42°,  Be.)  and  220  grs.  concentrated  sulphuric  acid. 
The  product  obtained  is  carefully  washed  with  water  and  very  di- 
lute alkali,  after  which  it  is  dried  and  subjected  to  fractional  dis- 
tillation. The  petroleum  hydrocarbons,  which  distil  up  to  150°, 
are  measured. 

(<£)  Fractional  distillation.  100  c.c.  crude  benzene  are  placed 
in  a  distilling  bulb  in  which  a  thermometer  is  placed  in  such  a 
manner  that  the  upper  end  of  the  mercury  reservoir  is  parallel  with 
the  lower  point  of  contact  of  the  exit  tube.  Connected  with  the 
distilling  bulb  is  a  condenser,  at  the  end  of  which  a  measuring 
cylinder  is  placed.  Heat  is  now  gently  applied,  and  the  tempera- 
ture at  which  the  first  drop  goes  over  is  recorded  as  the  beginning 
of  boiling.  Distillation  is  continued  rapidly  and  yet  in  such  a 
manner  that  the  drops  may  be  counted  as  they  run  into  a  cylinder. 
The  volume  of  the  distilled  fluid  is  read  off  every  5°.  At  100° 
the  flame  is  removed,  the  tube  is  allowed  to  drain,  and  the  volume 
of  the  distillate  is  recorded.  Thereupon  distillation  is  continued 
until  complete. 

The  following  table  shows  the  course  of  distillation  of  90,  50 
and  30  per  cent,  benzene  : 


Amount  Distilled  in  c.c.  up  to 

yj 

Cf.    »•      p  . 

q                  ./-          p 

85° 

900 

95° 

100° 

105° 

"5° 

120° 

90  per  cent. 
50      " 

82° 
88° 

20 

72 

5 

84 
30 

9° 
5o 

?5 
64 

t 

94 

.882 
.880 

30      •" 



... 

2 

12 

30 

42 

92 

90 

.875 

2.  Crude  Xylol. 

Determination  of  the  three  xylols  according  to  Lewinstein. — The 
method,  which  is  little  used,  practically  depends  on  the  difference 


166  CHEMICAL-TECHNICAL    ANALYSIS. 

in  behavior  of  these  substances  with  dilute  nitric  acid,  and,  further- 
more, with  cone,  and  fuming  sulphuric  acid. 

100  c.c.  crude  xylol  are  boiled,  while  constantly  agitated,  with 
40  c.c.  nitric  acid  (sp.  gr.  1.4)  and  60  c.c.  water  for  ^— i  hour. 
As  soon  as  the  evolution  of  red  fumes  has  ceased,  the  acid  is  sepa- 
rated from  the  hydrocarbons  in  a  separatory  funnel.  The  latter  are 
washed  with  dilute  alkali  and  distilled  in  a  current  of  steam. 

The  solution  of  the  hydrocarbons  (# )  in  the  distillate,  consisting 
of  metaxylol  and  hydrocarbons  of  the  fatty  series,  is  measured  and 
thereupon  shaken  for  a  half-hour  with  i  ^  times  the  volume  cone, 
sulphuric  acid.  Metaxylol  is  thereby  dissolved  as  sulphonic  acid, 
whereas  the  aliphatic  hydrocarbons  remain.  If  their  volume  (b} 
be  deducted  from  the  previous  volume  (#),  the  difference  (a-b) 
will  equal  the  metaxylol  present. 

To  determine  the  paraxylol,  100  c.c.  crude  xylol  are  shaken  for 
half  an  hour  with  120  c.c.  cone,  sulphuric  acid.  Ortho-  and  meta- 
xylol dissolve  as  sulphonic  acids.  When,  upon  further  addition  of 
sulphuric  acid,  the  latter  remains  colorless,  the  volume  of  the  un- 
dissolved  oil,  which  consists  of  paraxylol  and  aliphatic  hydrocar- 
bons, is  read  off.  Let  this  ==  c.  The  oil  is  now  drawn  off  from 
the  acid  and  shaken  with  an  equal  volume  of  fuming  sulphuric  acid, 
containing  20  per  cent,  anhydride.  Paraxylol  dissolves  and  the 
fatty  hydrocarbons  remain  unattacked.  If  their  volume  =  d,  then 
the  difference,  c-d,  will  yield  the  amount  of  paraxylol  present. 

If  the  sums  of  the  volume  percentages  of  meta-  and  paraxylol 
and  the  aliphatic  hydrocarbons  be  added,  and  their  sum  subtracted 
from  100,  the  difference  will  represent  orthoxylol. 

3.  Crude  Anthracene. 

The  determination  of  anthracene  by  the  method  of  Luck  (modi- 
fied by  Meister,  Lucius  and  Briining)  depends  on  the  property  of 
anthracene  to  yield  anthraquinone  on  oxidation  with  chromic  acid 
in  acetic  acid  solution.  The  latter  compound  is  not  attacked  by 
further  action  of  chromic  acid  and  of  sulphuric  at  100°.  On  the 
contrary,  the  other  constituents  of  anthracene  (acenaphthene,  fluo- 
rene,  phenanthrene,  carbozol,  fluoranthene,  etc.),  are  either  com- 
pletely destroyed  or  converted  into  sulphonic  acids,  which  are  solu- 
ble in  water  or  alkalies,  i  gr.  crude  anthracene  is  covered  with 


CRUDE    CARBOLIC    ACID.  167 

45  c.c.  glacial  acetic  acid  in  a  500  c.c.  flask.  The  flask  is  pro- 
vided with  a  double-bored  stopper,  through  one  opening  of  which 
a  separatory  funnel  is  inserted,  while  through  the  other  there  issues 
an  adapter,  which  is  connected  with  a  condenser.  To  the  boiling 
solution  of  anthracene,  15  grs.  chromic  acid  in  10  c.c.  glacial 
acetic  acid  and  10  c.c.  water  are  gradually  added.  The  chromic 
acid  is  added  at  intervals  of  2  hours.  The  solution  is  boiled  2 
hours,  stood  aside  for  12  hours,  diluted  with  400  c.c.  water,  and 
after  3  hours  is  filtered  from  the  separated  anthraquinone.  This 
is  washed  first  with  pure  water,  then  with  boiling  alkali,  and 
finally  again  with  water.  It  is  then  rinsed  from  the  filter  into  a 
small  flat  porcelain  dish.  The  water  is  evaporated,  and  the 
residue,  after  being  dried  at  100°,  is  heated  on  a  water-bath  with 
10  times  the  volume  of  fuming  sulphuric  acid  (68°  Be.).  The 
solution  so  obtained  is  allowed  to  stand  for  12  hours  in  a  moist 
place,  is  diluted  with  200  c.c.  cold  water,  and  the  pure  anthra- 
quinone formed  is  filtered  off.  The  latter  is  washed  as  before, 
rinsed  into  weighed  capsules,  dried  at  100°  and  weighed.  There- 
upon the  anthracene  is  volatilized  by  heating,  and  any  remaining 
ash  is  deducted  from  the  weight  first  obtained.  The  anthraquinone 
so  found  is  then  calculated  into  anthracene.  207.5  anthraquinone 
=  177.58  anthracene. 

4.  Crude  Carbolic  acid. 

Determination  of  phenol. — 120  grs.  crude  acid  are  distilled  from 
a  small  bulb,  which  is  attached  to  a  condenser,  until  about  8  grs. 
remain.*  The  distillate  is  dissolved  in  ether  and  shaken  out  with 
10  per  cent,  caustic  soda  in  a  separatory  funnel.  The  ethereal 
layer  is  washed  several  times  with  dilute  alkali,  and  the  aqueous 
layer  is  washed  several  times  with  ether.  The  united  alkaline 
extractions  are  decomposed  with  hydrochloric  acid  (i  :  i),  which 
is  added  to  acid  reaction,  and  extracted  with  ether.  After  the 
ethereal  solutions  have  been  washed  with  water  and  the  acid  liquid 
with  ether  in  a  separatory  funnel,  the  ethereal  solutions  are  placed 
in  a  weighed  flask.  The  ether  is  distilled  off  as  far  as  possible,  and 

*  This  procedure  is  suitable  because  the  subsequent  extraction  with  ether  is 
more  easily  accomplished,  and  a  sharper  separation  of  the  two  layers  is  obtained. 


168  CHEMICAL-TECHNICAL    ANALYSIS. 

the  last  traces  are  removed  by  attaching  the  flask  to  a  dephlegmator 
or  Linnemann  column  and  heating  the  same  over  a  wire  gauze  until 
an  inserted  thermometer  indicates  above  100°.  The  contents  are 
then  allowed  to  cool  and  are  weighed,  together  with  the  flask. 

5.  Dimethyl  Aniline. 

The  approximate  determination  of  monomethyl  aniline  can  be 
accomplished  by  the  rise  in  temperature  on  mixing  with  an  equal 
volume  of  acetic  anhydride. 

Every  degree  rise  in  temperature  corresponds  to  approxi- 
mately ^  per  cent,  monomethyl  aniline.  On  mixing  pure  di- 
methyl aniline  with  acetic  anhydride,  a  depression  of  )^0  is  ob- 
served. Each  test  requires  4  c.c. 

The  monomethyl  aniline  may  be  more  exactly  determined  by  the 
method  of  Nolting  and  Boasson  by  allowing  nitrous  acid  to  act  on 
the  product.  Monomethyl  aniline  is  thereby  converted  into  ether- 
soluble  methyl-phenyl-nitroso  amine  C6H5N  (NO)  (CH8),  whereas 
dimethyl  aniline  hydrochloride  is  converted  into  the  hydrochloride 
of  nitroso  dimethyl  aniline  C6H4(NO).N  (CH3).  HC1,  which  can- 
not be  extracted  by  ether  from  its  aqueous  solution.  According 
to  Nietzki,  30  grs.  dimethyl  aniline  are  dissolved  in  80  grs.  cone, 
hydrochloric  acid  and  about  y2  liter  water.  The  solution  is  well 
cooled  and  38  grs.  sodium  nitrite  are  run  in.  After  a  while  the 
solution  is  repeatedly  extracted  with  ether,  the  ethereal  solutions 
are  united,  the  ether  is  evaporated  off,  and  the  residual  oil  is  dried 
over  sulphuric  acid  and  weighed.  The  nitroso  amine  found,  when 
multiplied  by  .786,  gives  the  monomethyl  aniline  originally  present. 


Appendix. 


A.  White  Paint  (White  Lead). 

A  WHITE  paint  consists  of  a  white  pigment  ground  in  a  suitable 
oil,  usually  linseed  oil.  A  very  common  form,  and  for  general 
uses  the  best,  is  that  termed  "  white  lead,"  which  is  essentially  the 
pigment  white  lead  2PbCO3.Pb(OH)2  ground  with  linseed  oil. 
Other  pigments,  not  necessarily  adulterants,  which  may  be  ad- 
mixed or  per  se  are  barium  sulphate,  lead  sulphate,  zinc  oxide,  zinc 
carbonate,  zinc  sulphide,  strontium  sulphate,  calcium  sulphate, 
calcium  carbonate,  magnesite,  kaolin  and  silica.  These  and  others 
are  brought  into  the  market  in  one  form  or  another  under  various 
names.  Mineral  oils,  rosin  oil,  etc.,  may  be  present  with  the  dry- 
ing oil  of  the  paint.  These  may  be  detected,  after  separation  from 
the  pigment,  by  other  methods  given  in  the  chapter  on  Oils. 

Analysis. 

In  a  small  Erlenmeyer  flask  about  5  grs.  paint  are  weighed  out. 
This  is  repeatedly  washed  by  decantation  with  pure  ether  until  a 
few  drops  of  the  latter  leave  no  non-volatile  residue  on  evapora- 
tion. The  residue  is  thrown  on  a  filter  or  else  freed  from  adher- 
ing traces  of  ether  by  a  current  of  air.  The  collected  ethereal  ex- 
tractions are  evaporated,  and,  after  expelling  the  last  traces  of  ether 
in  the  usual  way,  the  residual  oil  is  weighed,  and  if  necessary  ex- 
amined. The  weight  of  the  residue  is  gotten  by  difference.  It  is 
then  subjected  to  analysis  by  the  following  scheme  (see  table  on  page 
170). 

The  residue  may  contain  PbSO4,  2PbCO3.Pb(OH)2,  BaSO4, 
CaSO4,  CaCO3,  BaCO3,  ZnCO3,'ZnO,  SiO2,  clay,  etc.  It  is  covered 
with  hot  acetic  acid,  diluted,  heated  and  filtered. 

B.  Manganese  Dioxide,  Bleaching  Lime,  Etc. 

The  simplicity  of  the  Lunge  nitrometer  (Fig.  i)  and  its  prin- 
ciple furnish  a  more  extended  use  of  the  same  in  quantitative  an- 


170 


CHEMICAL-TECHNICAL    ANALYSIS. 


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MANGANESE    DIOXIDE.  171 

alysis.  In  fact  a  quantitative  method  is  insured  wherever,  under 
convenient  conditions,  an  equivalent  in  form  of  gas  is  evolved  by 
the  chemical  decomposition  of  a  substance.  Such  substances  are 
manganese  dioxide,  bleaching  lime,  hydrogen  peroxide,  etc.,  etc. 
For  the  purpose  of  the  estimation  of  their  value  either  the  original 
nitrometer  (Fig.  i),  or,  even  more  convenient,  the  later  form  of 
gasvolumeter,  may  be  used.  A  slight  modification,  a  generator 
similar  in  principle  to  that  in  Fig.  9,  is  used.  A  plain,  thick, 
wide-necked  bottle,  with  a  perforated,  well-ground  stopper,  which  is 
provided  with  a  small  internal  receiver,  is  connected  with  the 
opening  in  the  stopcock  (Fig.  i)  by  the  stout  rubber  tube.  Since 
the  volume  read  off  is  displaced  air,  the  zero  point  taken  need  not 
necessarily  be  the  zero  mark  on  the  apparatus.  The  apparatus  is 
adjusted  as  usual,  and  the  readings  are  reduced  to  o°  C.  760  mm. 
pressure.  Decomposition  is  complete  in  the  generator  when  in 
agitating  the  latter  the  mercury  meniscus  does  not  change. 

1.  Manganese  Dioxide. 

When  manganese  dioxide,  in  very  finely  divided  condition,  and 
hydrogen  peroxide  are  brought  together  in  acid  solution  the  de- 
composition which  ensues  is  expressed  by  the  equation 


Since  i  c.c.  oxygen  at  o°  C.  760  mm.  weighs  1.43003  mg., 
every  c.c.  oxygen  obtained  when  reduced  to  the  same  conditions 
will  equal  .00389  gr.  MnO2. 

Operation.  —  About  .19  gr.  substance  is  placed  in  the  genera- 
tor, and  shaken  with  dilute  sulphuric  acid  in  order  to  decom- 
pose any  carbonates  present.  Somewhat  more  than  3.7  c.c.  of  a 
2  percent,  hydrogen  peroxide  solution  (i.e.,  the  theoretical  amount 
for  the  above  quantity  of  substance)  are  poured  into  the  little  cup 
which  is  placed  in  the  generator.  The  mercury  in  both  tubes  is 
placed  on  the  same  level  and  read  off.  The  cup  on  (a)  and  the 
side  tube  are  put  into  communication  when  the  generator  flask  is 
attached.  The  stopcock  is  then  turned  to  establish  communication 
between  the  eudiometer  (a)  and  the  generator,  whereby  no  change 
in  the  mercury  level  must  occur.  The  contents  of  the  generator 
are  then  mixed,  and  after  decomposition  has  taken  place  the  mur- 


172  CHEMICAL-TECHNICAL    ANALYSIS. 

cury*  levels  are  again  adjusted,  the  apparatus  is  allowed  to  stand 
for  a  while,  f  the  volume  is  read  off,  reduced,  and  calculated  into 
manganese  dioxide  by  means  of  the  above  data. 

2.  Bleaching-  Lime. 

Reaction  takes  place  between  bleaching  lime  and  hydrogen  per- 
oxide as  follows  : 


CaOCl2+H2O2  —  CaCl2+H2 

Therefore  every  volume  of  oxygen  evolved  represents  an  equal 
volume  of  "active  "  chlorine  in  the  bleaching  lime.  The  latter  is 
prepared  for  use  as  usual  by  weighing  7-8  grs.  in  a  weighing  bottle. 
The  contents  are  poured  into  a  porcelain  mortar,  rubbed  to  a  thick 
paste,  diluted  with  water  to  a  thin  paste  and  poured  into  a  liter 
flask  through  a  funnel.  The  flask  is  filled  to  the  mark.  40-50  c.c. 
of  this  turbid  solution  are  used.  The  hydrogen  peroxide,  which  is 
placed  in  the  little  cup,  is  first  made  alkaline  by  careful  addition  of 
sodium  hydrate.  The  operation  is  conducted  as  above. 

3.  Hydrogen  Peroxide  and  Permanganate. 

Since  5  H2O2+2  KMnO4-f  3  H2SO4=8H2O  +  K2SO4-f  2MnSO4+ 
5O2,  the  value  of  either  one  or  the  other  can  be  determined  by  using 
an  excess  of  one  or  the  other  in  the  operation.  Then  every  c.c. 
oxygen  reduced  to  o°  C.  760  mm.  =:  2.8243  mg.  KMnO4  or 
1.5194  mg.  H2O2,  as  the  case  may  be. 

C.  Asphalt  and  Asphaltic  Substances. 

Under  this  heading  may  be  understood  natural  bitumens,  varying 
in  physical  properties  from  hard,  resonant,  vitreous  masses  to  soft, 
sticky  masses.  The  former  are  known  under  the  technical  name  of 
asphalt,  and  the  latter  under  the  name  of  maltha.  With  more  or 
less  mineral  matter,  which,  likewise,  can  vary  in  physical  and  chem- 
ical composition,  they  belong  to  the  product  which,  when  admixed 
with  suitable  constituents  and  subjected  to  various  processes,  form 
the  basis  of  artificial  paving.  Little  is  known  regarding  the  origin 
of  these  substances  and  the  nature  of  their  organic  constituents. 

*  Instead  of  mercury,  a  salt  solution  or  water  may  be  employed. 
f  As  soon  as  temperature,  etc.,  are  uniform,  on  standing,  hydrogen  peroxide 
evolves  oxygen. 


ASPHALT    AND    ASPHALTIC    SUBSTANCES.  173 

A  very  exhaustive  and  interesting  research  is  that  of  Clifford  Rich- 
ardson,* who  has  shown  that  the  bitumen  proper  consists  of  hydro- 
carbons of  the  series  Cn  H2n,  and  probably  of  lower  series ;  that 
they  contain  very  little,  if  any,  oxygen,  and  that  maltha  is  con- 
verted into  asphaltum  by  reactions  in  which  sulphur  plays  a  prom- 
inent part.  He  has  also  subjected  various  isolated  constituents  to 
the  usual  processes  of  examination  of  oils,  and  has  materially  added 
to  the  data  used  in  the  analysis  of  asphalt. 

A  general  description  of  analysis  will  be  given,  together  with  a 
few  analytical  results.  The  analysis  includes  the  estimation  of 
water,  substances  soluble  in  petroleum  ether  or  petrolene,  sub- 
stances soluble  in  carbon  bisulphide  or  turpentine,  called  asphaltene, 
organic  matter  not  bitumen,  and  mineral  matter.  The  method  de- 
scribed and  results  appended  are  those  of  Laura  A.  Linton  :f 

(<?)  Water.  2-5  grs.  substance,  divided  as  finely  as  possible  or 
spread  over  as  large  a  layer  as  possible,  are  dried  over  sulphuric 
acid  in  a  desiccator,  or,  better,  in  a  current  of  dry  air  at  a  temper- 
ature not  exceeding  50°  C.  The  substance  is  reweighed,  and  the 
remaining  results  are  based  on  anhydrous  material. 

(^)  Petrolene.  2-5  grs.  substance,  depending  on  the  amount  of 
bitumen  present,  are  weighed  on  a  tared  filter  paper,  which  has 
been  fitted  into  a  much  larger  funnel,  provided  on  its  exit  tube 
with  a  stopcock.  The  contents  are  repeatedly  extracted  with 
petroleum  ether  every  'few  minutes.  To  remove  the  last  traces 
digest  several  hours.  The  filter  and  contents  and  counterpoise  are 
dried  in  a  steam-bath  and  weighed.  The  loss  in  weight  represents 
petrolene. 

(c}  Asphaltene.  i.  The  filter  and  contents  are  replaced  on  the 
funnel  and  extracted  in  a  similar  manner  with  turpentine.  After 
complete  exhaustion,  which,  at  times,  is  tedious,  the  contents  are 
washed  with  alcohol,  dried  and  weighed  as  before.  The  difference 
represents  asphaltene  soluble  in  turpentine. 

2.  The  process  is  repeated,  using  chloroform  for  extraction. 
The  difference  represents  asphaltene  soluble  in  chloroform. 

The  three  fractions  are  summed  up  as  "  total  bitumen." 

*  Journal  Soc.  Chem.  Industry,  Vol.  xvii.,  p.  13  (1898). 

f  Journal  Amer.  Chem.  Society,  Vol.  xvi.,  p.  809;  Vol.  xviii.,  p.  275. 


174 


CHEMICAL-TECHNICAL    ANALYSIS. 


(d)  Mineral  matter.  The  residue  is  ignited  in  a  platinum  dish, 
cooled  and  weighed.  In  case  carbonates  are  present,  the  ash  must 
be  recarbonated  by  ignition  with  ammonium  carbonate. 

(<?)  Matter  not  bitumen  is  that  which  remains  when  the  sum  of 
the  percentages  obtained  in  a,  b,  c  and  */are  deducted  from  100, 


c 
5 

62 

0   C 

|g 

S  -• 

8 

i 

1 

|| 

II 

4) 

e 

1 

S.2  c 

£si 

!! 

1 

o 

i 

|*S 

£  jj 

PQ 

III 

•|M 

1 

PLH 

H^ 

uta 

1 

MO 

c 

H 

«^ 

Oc 

i 

Trinidad  asphaltum.,... 

35-40 

I23 

5.29 

17.59 

52.99 

i  :  10 

10.96 

36.1 

Scyssel    asphaltic    rock 

(Eastern  France)*  

7-49 

3-95 

•37 

4.32 

1  1.8 

1:31 

88.2 

Sandstonef       asphaltic 

rock      (  locality      un- 

known)   

5.12 

2 

27 

2.27 

7.79 

.75 

01.86 

») 

/ 

/  *O-7 

*/  *? 

-y     »v^ 

Water. 
86.87 


D.  Food  Stuffs. 

Under  this  head  will  be  considered  a  few  types  of  food  stuffs, 
such  as  milk,  flour,  coffee  and  pepper.  Armed  with  the  general 
methods  it  is  quite  possible,  using  such  modifications  and  precau- 
tions as  good  judgment  dictates,  to  conduct  the  investigation  of 

other  substances. 

1.  Milk. 

1.  The  average  composition  of  new  cow's  milk  is  : 

Fat.  Casein.         Albumin.     Milk  Sugar.          Ash.  Solids. 

3.50  3.98  .77  4.00  .17  13.13 

Its  average  specific  gravity  is  1.029-1.039. 

2.  Products  made  from  cow's  milk  may  contain  one,  several  or 
all  of  these  constituents,  with  or  without  necessary  additions.     They 
depend  on  the  operation  which  the  milk  undergoes,  and  the  nature 
and   quantity  of  material  added    to   yield   the  products    desired. 
Under  this  head  come :   a.   Cream,  skim-milk,   buttermilk,   curd, 
whey,  butter,  cheese,  milk  sugar,  casein,  koumiss,     b.  Condensed 
milk,  preserved  milk,  lactated  foods. 

*  This  belongs  to  the  class  of  asphaltic  limestones,  and  can  contain  as  much  as 
91.3  per  cent,  calcium  carbonate, 
f  Analysis  by  author. 


FOOD    STUFFS.  175 

3.  Finally,  milk  may  contain  alteration  products,  such  as  lactic 
acid,  etc.,  and  preservatives,  such  as  borax,  salicylic  acid,  bicar- 
bonate of  soda,  ultramarine,  etc.  Practically,  the  main  adulterant 
used  is  water. 

A  description  of  an  analysis  embracing  all  these  substances  is  for 
the  present  purpose  too  extended. 

For  a  complete  analysis  of  milk  the  following  apparatus  should 
be  prepared,  and  if  possible  all  parts  of  the  analysis  should  be  con- 
ducted at  once : 

1.  Sp.  gr.  hydrometer,  hydrostatic  balance  or  pyknometer. 

2.  Porcelain    or  platinum  capsule    of  about    50    c.c.    capacity, 
weighed  together  with  ignited  bar-sand  and  a  small  glass  rod. 

3.  Small  weighed  platinum  dish  or  crucible. 

4.  A  weighing  bottle  of  convenient   form   and  two  separately 
dried  and  weighed  filter  papers. 

Operation, — The  specific  gravity  is  taken  at  15.5°  C.  —  60°  F. 

(0)  Solids.  10  c.c.  milk,  the  weight  of  which  is  equal  at  15.5° 
C.  to  the  sp.  gr.  with  the  decimal  point  moved  one  place  to  the 
right,  are  placed  in  the  platinum  dish  with  the  sand,  are  evaporated 
to  dryness  with  occasional  stirring  on  a  water-bath,  and  are  finally 
dried  at  105°  in  an  air-bath  to  constant  weight. 

(£)  Ash.  The  contents  of  the  second  crucible,  10  c.c.,  are 
evaporated  to  dryness,  incinerated  and  weighed.  In  more  exact 
work  the  dry  mass  is  simply  charred,  washed  with  water  and  fil- 
tered. After  incinerating  the  charred  mass,  the  washings  are  added 
and  evaporated  to  dryness.  In  this  case  volatile  portions,  such  as 
salt,  are  retained. 

(c)  Fat,  casein  and  albumin.  Hoppe-Seyler  method.  10  c.c.  milk 
are  diluted  to  50  c.c.  in  a  small  beaker  with  water.  The  solution  is 
warmed  to  45°  and  1-2  c.c.  of  10  per  cent,  acetic  acid  are  added. 
Casein  and  fat  are  precipitated  in  form  of  curd,  whereas  albumin 
remains  in  solution.  The  precipitate  is  filtered  on  a  weighed  filter, 
dried  at  105°  in  a  weighing  bottle  and  reweighed.  The  weight  of 
bottle+filter  deducted  from  the  latter  weight  gives  the  weight  of 
casein  and  fat. 

The  filter  is  placed  in  a  suitable  form  of  extractor,*  which  is  put 

*  The  Thorn  extractor  is  very  suitable. 


176 


CHEMICAL-TECHNICAL    ANALYSIS. 


into  operation  for  6-8  hours.  The  niter  and  contents  are  then 
placed  in  a  perfectly  clean  weighing  bottle,  dried  at  105°,  and  re- 
weighed.  Bottle  plus  filter  plus  casein  minus  bottle  plus  filter 
gives  the  weight  of  casein.  Casein  plus  fat  minus  casein  =  fat. 
The  filtrate  containing  albumin  is  boiled  for  several  minutes.  The 
precipitate  formed  is  collected  in  another  weighed  filter,  is  washed, 
dried  and  weighed. 

(*/)  Milk  sugar.  Ritthausen  method.  10  c.c.  milk  are  diluted 
to  about  100  c.c.  with  water  in  a  beaker  of  about  200  c.c.  capacity. 
Everything  except  soluble  salts  and  milk  sugar  is  precipitated  by 
the  addition  of  10  c.c.  copper  sulphate  solution  (69.28  grs.  copper 
sulphate  per  liter)  and  sufficient  sodium  hydrate  solution  to  in- 
completely precipitate  the  copper.  The  precipitate  formed, 
together  with  liquid,  is  thrown  on  a  ribbed  filter  of  about  200  c.c. 
capacity,  and  filtrate  and  washings  are  collected  in  a  500  c.c.  flask 
and  diluted  to  the  mark.  200  c.c.  filtrate  are  boiled  with  25  c.c. 
each  of  Fehling's  solutions  for  6  minutes  and  the  cuprous  oxide 
formed  is  treated  as  on  page  86.  The  milk  sugar. is  found  by 
reference  to  the  following  table : 

Table  for  Milk  Sugar. 


Weight  of  Copper. 

Milk  Sugar. 

ioo  Parts  of  Milk  Sugar 
Precipitate  of  Copper 

Reduction  Ratio. 

mg. 

mg. 

Oxide. 

392.7 

300 

130.9 

:7-43 

363.6 

275 

132.2 

:7-5° 

333-0 

250 

133.2 

:7-56 

300.8 

225 

133-7 

:7-59 

269.6 

200 

134.8 

:7-65 

237-5 

175 

135-7 

17.70 

204.0 

ISO 

136.0 

=  7-72 

171.4 

I25 

I37.I 

:7-78 

138.3 

100 

138.3 

:7-85 

All  weights  of  constituents  are  calculated  into  per  cent. 

For  very  many  purposes  only  one  or  two  of  these  constituents 
are  wanted.  In  the  technical  analysis  of  milk,  adulteration  with 
water  and  by  skimming  are  guarded  against  by  estimation  simply  of 
specific  gravity,  total  solids  and  fat.  Necessarily  quicker  and 
shorter  methods  are  required.  For  the  estimation  of  fat  the  method 


BUTTER.  177 

of  Leffmann-Beam*  and  Chevalier  f  are  there  substituted.  These, 
however,  require  special  forms  of  apparatus. 

Albuminoids  may  be  determined  by  the  Kjeldahl  (see  p.  74) 
or  some  modified  method,  such  as  the  Gunning  method  (see  p.  182), 
or  by  combustion  with  soda-lime  (see  p.  74).  In  any  case  nitro- 
gen is  calculated  from  ammonia  obtained,  and  is  multiplied  by  the 
factor  6.25  to  obtain  total  albuminoids. 

Condensed  milk. — This  may  or  may  not  contain  cane  sugar.  The 
latter  is  a  common  form  and  contains  about  25.51-30.05  percent, 
water,  6. 60-10.08  per  cent,  fat,  44.47-53.27  percent,  cane  and  milk 
sugars,  10.11-12.04  per  cent,  casein,  and  1.80-2.09  Per  cent« 
salts.  J  For  analysis,  definite  portions  are  diluted  and  analyzed  as 
heretofore.  Cane  sugar  will  be  present  with  the  milk  sugar,  and 
may,  if  necessary,  be  determined  after  inversion.  (See  p.  86. ) 

2.  Butter. 

Butter  consists  of  butter  fat,  curd,  water,  milk  sugar  and  salt. 
A  complete  analysis  is  conducted  as  follows  : 

About  5  grs.  uniform  sample  are  weighed,  together  with  a  suitable 
weighing  bottle,  which  has  previously  been  weighed.  A  short 
glass  rod,  flattened  at  one  end,  is  weighed  in  also.  With  this  im- 
provised spatula,  about  half  the  butter  is  placed  on  a  tared  filter 
paper  and  extracted  with  chloroform  in  an  extractor.  The  weigh- 
ing bottle,  spatula  and  remaining  butter  are  reweighed,  and  the 
quantity  used  is  gotten  by  difference.  The  quantity,  number  2, 
remaining  in  the  bottle  is  also  calculated. 

(a)  Fat.  Quantity  i  is  extracted  for  a  period  of  about  6  hours  with 
chloroform.  The  curd,  milk  sugar  and  salt,  plus  filter  paper,  are 
dried  and  weighed,  and  their  combined  weight,  deducted  from 
quantity  i,  gives  fat,  plus  water,  which  is  calculated  into  per  cent. 
In  order  to  obtain  the  percentage  of  fat,  the  water  percentage  found 
in  (r)  is  deducted. 

(/£)  Curd,  salt  and  milk  sugar.  The  residue  on  the  filter  con- 
sists of  milk  sugar,  salt  and  curd.  It  is  washed  with  hot  water  and 
the  collected  washings  are  diluted  to  a  definite  volume.  Aliquot 

*  Leffmann-Beam  Milk  Analysis, 
f  Becke,  Milch  Priifungs-Methoden,  p.  40. 
J  Battershall.     Food  Adulterations  and  Its  Detection,  p.  53. 
12 


178  CHEMICAL-TECHNICAL    ANALYSIS. 

portions  are  used  for  milk  sugar  (see  above)  and  salt  (p.  177)  deter- 
minations. The  filter,  plus  curd,  is  dried  at  105°  and  reweighed. 
The  curd  is  found  by  deducting  the  weight  of  filter  paper  from  the 
above  weight. 

(V)  Water.      Quantity  2  is  dried  to  constant  weight. 

All  results  are  calculated  to  percentage. 

Examination  of  butter  fat  is  most  important,  as  this  is  the  only 
means  of  distinguishing  genuine  butter  from  substitutes.  For  this 
purpose  the  filtered  fat  is  used,  and  the  constants  determined  are 
viscosity.*  Reichert-Meissl  number,  p.  117;  iodine  number,  p. 
in  ;  Kottstorfer  number,  p.  no.  The  behavior  in  the  refracto- 
meter  is  also  a  valuable  criterion.  For  constants  see  p.  113. 

Tea,  Coffee  and  Cocoa. 

The  analysis  of  genuine  tea  and  coffee  is  rarely  conducted  for 
the  purpose  of  determining  their  values  as  producers  of  beverages. 
On  the  other  hand,  the  estimation  of  caffein  in  the  manufacture  of 
that  substance  and  the  disclosure  of  foreign  admixtures  of  organic 
nature,  foreign  leaves  in  the  case  of  tea,  foreign  and  artificial  beans 
in  the  case  of  coffee,  coloring  matter  (facings),  Prussian  blue,  tur- 
meric, indigo,  etc.,  and  of  substances  of  inorganic  nature,  mineral 
matter,  weighting  material,  etc.,  often  demand  investigation  of 
chemical  and  microscopic  nature,  f 

3.  Tea. 

The  analysis  of  twenty -three  teas  in  Russian  commerce  by  Drag- 
gendorf  gave  a  mean  : 

Per  cent. 
Water,          .........         10.00 

Extract,        .........         32.67 

Theine,  caffein,  •.         .         .          .         .          .         .         .  1.90 

Tannin  (four  determinations),         .....          11.42 

Ash, •  .          .          .  6.23 

(#)  Moisture.  1—2  grs.  powdered  sample  are  dried  to  constant 
weight  in  a  weighing  bottle. 

(^)  Extract.  5  grs.  sample  are  boiled  with  500  c.c.  water  for 
one  hour  on  a  reflux  condenser.  An  aliquot  portion  is  drawn  off, 

*  Dr.  Neuman  Wender,  Journal  Amer.  Chem.  Society,  Vol.  xvii.,  p.  719. 
f  Foods,  Composition  and  Analysis.     A.  W.  Blyth. 


COFFEE. 


179 


evaporated  to  dryness  and  weighed.  Adulteration  with  spent  leaves 
lowers  the  percentage  of  extract.  The  determination  is  not  very  re- 
liable, because  genuine  tea  can  contain  from  26-40  per  cent,  extract. 
(<:)  Theine,  caffein.  5  grs.  sample  are  boiled  on  a  reflux  with 
water  for  several  hours.  The  liquid  and  leaves  are  evaporated  with 
some  magnesia  to  pasty  condition.  This  is  exhausted  with  chloro- 
form, and  the  latter  is  separated  and  distilled  off.  The  residue  is  dis- 
solved in  a  little  boiling  water,  evaporated  to  dryness  at  a  gentle 
heat,  and  weighed. 

(*/)  Tannin.  The  process  (p.  149)  may  be  employed.* 
(<?)  Ash.  1-5  grs.  sample  are  incinerated  in  a  platinum  dish. 
There  is  no  danger  of  volatilization  since  the  leaves  readily  incin- 
erate at  low  temperatures.  The  ash  is  cooled  and  weighed.  It 
should  equal  5.17-7.02  per  cent.  It  is  lixiviated  with  hot  water, 
and  the  soluble  portion  is  removed  by  filtration  on  an  ashless  filter. 
Filter  and  contents  are  replaced  in  the  dish,  ignited,  cooled  and 
weighed.  The  insoluble  portion  is  gotten  directly,  and  the  soluble 
portion  is  obtained  by  difference.  The  former  should  be  2.64-4.22 
per  cent,  and  the  latter  1.33-2.87  percent.  Another  characteristic 
is  about  i  per  cent,  manganous  oxide. 

4.  Coffee. 

The  analysis  comprises  the  estimation  of  water,  caffein,  fat,  fiber, 
ash.     The  following  averages  were  obtained  by  Konig  : 


T3 

B 

• 

O 

c 

I 

"v> 

'i 

1 

Sugar. 

M 

I 

0 

Per 
cent. 

Per 

cent. 

Per 
cent. 

Per 

cent. 

Per 

cent. 

Per 
cent. 

Per  cent. 

Unroasted  coffee  
Roasted  coffee  

11.23 
1.15 

13.27 
1448 

18.17 
19.89 

3-92 
4  75 

12.07 
13.98 

I.2I 

1.24 

(      Telus 

.66  •<   gums  and 

(^    dextrin. 

Water,  ash  and  caffein  are  estimated  as  in  tea. 

(a)  Fat.      2-3   grs.    finely  powdered  sample   are   placed   in  an 


*  A  more  reliable  method  is  that  of  Councler  and  Schroeder,  Zeit.  fur  anal. 
Chem.,  25,  121. 


180  CHEMICAL-TECHNICAL    ANALYSIS. 

extractor  with  petroleum  ether  and  extracted  for  several  hours.  The 
petroleum  ether  is  distilled  off,  and  the  residue,  which  is  quite 
pure,  is  dried  and  weighed. 

Fiber* — 2  grs.  substance  are  washed  several  times  by  decantation 
with  ether  and  boiled  for  ^  hour  on  a  reflux  with  200  c.c.  1.25  per 
cent,  sulphuric  acid  in  an  Erlenmeyer  flask.  The  solution  is  filtered 
through  linen,  and  the  filtrate  is  refiltered  through  a  Gooch  crucible. 
The  two  residues  are  washed,  reunited  and  boiled  in  the  same  flask 
with  200  c.c.  1.25  per  cent,  caustic  soda.  Filtration  and  washing 
are  conducted  as  before.  The  contents  of  the  linen  are  washed 
with  alcohol  into  the  crucible  and  then  washed  with  ether,  dried  at 
110°  and  weighed.  It  is  then  incinerated  and  the  ash  is  deducted. 
Adulterants  may  be  inorganic  coloring  matter,  etc.,  in  which  case, 
the  percentage  and  nature  of  the  ash  would  give  some  indication. 
Organic  adulterants  consist  of  artificial  beans,  which  are  usually 
made  of  flour,  chicory  and  sugar  caramel,  which  forms  on  the 
roasted  bean  when  the  unroasted  bean  is  treated  with  sugur  solu- 
tions. Roughly,  the  presence  of  the  first  named  may  be  detected 
by  covering  the  sample  with  water.  Natural  beans  float,  whereas 
artificial  beans  sink.  The  test  is  not  always  conclusive.  The  coffee 
bean  contains  no  starch,  and  therefore  flour  in  any  form  can  be 
recognized  by  the  starch  reaction.  Chicory  maybe  suspected  when 
the  ash  contains  much  over  .03  per  cent,  chlorine.  Careful  incin- 
eration is  advised  in  this  case.  Burnt  sugar  or  caramel  is  detected 
by  the  rapid  darkening  of  water  on  which  a  little  coffee  is  sprinkled. 
Comparative  microscopic  examinations  afford  the  safest  clues. 

5.  Cocoa  and  Chocolate. 

Cocoa,  the  ground  product  of  the  decorticated  cocoa  bean, 
forms  the  basis  of  all  cocoa  preparations.  The  average  composi- 
tion, according  to  J.  A.  Wanklyn,  is  : 

Per  cent. 

Fat  (cocoa  butter), 50.00 

Theobromin,         .  .         .         .         .          .         .          .  1.50 

Starch,         .     •    .  .         .         .         ,         .         .         .  10.00 

Albumin,  etc.,     .  .         .         .         .                           .  18.00 

Gum,  .         .         .  ..        .         .         .         .         .         .  8.00 

Coloring  matter,   .  .         .'      .         .         .         ;         .  2.60 

Water,          . 6.00 

Ash,    .         .         . 3.60 

*  U.  S.  Dept.  Agriculture  Bulletin,  No.  13. 


COCOA   AND    CHOCOLATE.  181 

When  incorporated  with  refined  sugar  it  forms  chocolate.  Fre- 
quently the  expressed  and  "defatted"  substance  is  used  for  the 
above.  Both  varieties,  mixed  with  various  kinds  of  starch,  sugar 
and  flavoring  extracts,  constitute  cocoa  preparations.  In  soluble 
cocoa  preparations  the  former  is  previously  defatted,  treated  with 
ammonia  to  destroy  the  cellular  structure,  and  then  with  necessary 
reagents  to  transform  the  albuminoids  to  a  soluble  form. 

The  use  of  the  above  substances  in  moderation  is  for  many 
reasons  allowable,  but  their  abuse  is  considered  adulteration.  Min- 
eral matter,  weighting  material,  etc.,  may  be  present  as  adulterants. 

The  analysis  embraces  the  determination  of  water,  fat,  starch, 
theobromin,  sugar,  nitrogenous  matter  and  ash. 

(a)  Water.  2-5  grs.  rasped  or  powdered  sample  are  dried  to 
constant  weight  at  105°. 

(&)  Fat.  2  grs.  rasped  or  powdered  sample  are,  if  necessary, 
mixed  with  sand  and  extracted  with  ether.  The  ether  is  distilled 
off  and  the  fat  is  dried  at  100°  and  weighed.  If  previous  "de- 
fatting"  and  addition  of  foreign  fat  be  suspected,  the  usual  constants 
are  determined.  The  iodine  number  of  genuine  cocoa  butter  is 
about  34,  Kottstorfer's  about  200. 

(V)  Sugar.  The  residue  from  (^)  is  extracted  with  cold  water  and 
an  aliquot  portion  is  inverted.  The  remaining  operation  is  as  on 
p.  86. 

(d)  Starch.     The  residue  from  (V)  is  boiled  with  water  and  in- 
verted.    In  an  aliquot  portion  of  the  solution  the  starch  is  deter- 
mined as  in  p.  99.      To  determine  the  nature  of  the  starch  a  mi- 
croscopic examination  is  necessary. 

(e)  Theobromin  is  determined  asunder  theine,  caffein  (p.  179), 
except  that  the  sample  is  first  defatted  with  petroleum  ether  and  the 
final  extraction  is  done  with  boiling  80  per  cent,  alcohol.     The 
residue  left  on  expelling  the  latter  is,  if  necessary,  purified  with 
petroleum  ether,  dried  and  weighed. 

(/)  Nitrogenous  matter  is  determined  by  the  Kjeldahl  process, 

p.  74- 

( g)  Ash.  5  grs.  sample  are  incinerated  in  a  platinum  dish  and 
weighed.  The  fact  that  the  dry  cocoa  bean  contains  about  1.5  per 
cent,  of  phosphoric  acid  is  of  importance. 


182  CHEMICAL-TECHNICAL    ANALYSIS. 

6.  Flour  and  Other  Cereals. 

The  analyses  comprise  the  determination  of  water,  ash,  starch, 
fat,  nitrogenous  matter,  water  extract  and  wood  fiber.  Adulterants 
would  mainly  be  present  in  form  of  inorganic  weighting  material. 

(#)  Water.  2-5  grs.  sample  are  dried  at  105°  to  constant 
weight. 

(£)  Ash.  2-5  grs.  sample  are  incinerated  in  a  platinum  dish, 
cooled  and  weighed.  Frequently  the  ash  is  difficult  to  free  from 
carbon  particles.  In  this  case  careful  addition  now  and  then  of 
crystals  of  pure  ammonium  nitrate  aids  the  incineration. 

(<r)  Starch  is  determined  after  inversion,  as  usual.  (See  p.  99.) 
From  the  copper  obtained,  that  produced  by  inversion  of  a  cold 
water  extract  of  an  equal  amount  of  flour  must  be  deducted.  The 
difference  is  then  calculated  into  starch. 

(*/)  Nitrogenous  matter,  which  consists  mainly  of  glutin,  is  de- 
termined as  on  p.  74,  or  by  a  modification  known  as  the  Gunning 
method.  This  differs  only  in  the  process  of  decomposition,  which 
requires  heating  with  30—40  c.c.  of  a  semi-fluid  mass,  obtained  by 
warming  two  parts  cone,  sulphuric  acid  and  one  part  ground  potas- 
sium sulphate.  The  liquid  is  heated  briskly  until  it  becomes  per- 
fectly clear.  In  the  remaining  operation  addition  of  sulphide  of 
sodium  is  unnecessary. 

(<?)  Fat.  5  grs.  dried  sample  are  extracted  with  ether  in  an  extrac- 
tor, and  after  expulsion  of  the  latter  the  residue  is  dried  and  weighed. 

(/)  Water  extract.  10  grs.  flour  are  covered  with  500  c.c. 
water  and  briskly  shaken.  250  c.c.  are  filtered  into  a  platinum 
dish,  evaporated  to  dryness,  dried  and  weighed.  The  residue, 
which  contains  sugar,  gum,  dextrin,  albumin  and  phosphate  of 
potash,  should  equal  about  5  per  cent.  On  ignition  it  should  con- 
sist entirely  of  potassium  phosphate.  In  a  portion  of  the  liquid,  corre- 
sponding to  the  flour  used  in  the  starch  determination,  the  reducing 
power  in  copper  units  is  determined  after  inversion.  (See  <:.) 

Of)  Wood  fiber.  The  determination  is  of  more  use  in  the  an- 
alysis of  whole  or  crushed  cereals.  The  determination  is  conducted 
as  on  p.  1 80. 

The  percentage  values  of  wheat  flour  are  by  no  means  constant. 
TOO  parts,  according  to  Wanklyn,  contain:  water  16.5  per  cent., 
fat  1.2  per  cent.,  glutin,  etc.,  12.0  per  cent.,  starch,  etc.,  69.6  per 
cent.,  ash  .7  per  cent. 


SPICES,    ETC. 


183 


Spices,  Etc. 

Unless  supplemented  by  a  careful  microscopic  examination  in  the 
search  for  adulterants  the  chemical  analysis  of  spices,  etc.,  is  of 
little  value  except  in  the  matter  of  discovering  the  addition  of  in- 
organic substances,  sand,  etc.  Water,  ash,  starch,  fat  (oils)  and 
fiber  determinations  furnish  the  analytical  data.  The  example 

selected  is  : 

7.  Pepper. 

Adulterations  in  form  of  various  ground  seeds,  dust,  sand,  ground 
husks  and  shells,  starch,  flour,  etc.,  etc.,  are  found  in  cheaper 
grades. 

(0)  Water.      2-5  grs.  sample  are  dried  at  105°  and  weighed. 

(£)  Ash.  The  residue  from  the  above  is  incinerated  and 
weighed. 

(<r)  Starch.  The  substance  is  first  washed  with  alcohol  and  then 
treated  precisely  as  under  starch  (p.  99.)  The  solution  is  accu- 
rately neutralized  and  diluted  to  500  c.c.  before  it  is  reduced  with 
Fehling's  solution. 

(//)  Fats,  etc.  i.  Total  ether  extract.*  2  grs.  sample  are  ex- 
tracted in  a  large  Soxhlet  apparatus  with  absolute  ether  for  24 
hours.  The  extract  is  washed  into  a  weighed  capsule  and  the 
ether  is  allowed  to  evaporate  spontaneously,  but  not  too  rapidly. 
It  is  then^iried  over  night  in  a  desiccator  and  weighed. 

2.  Volatile  oil.  The  residue  is  heated  to  no°-for  several  hours 
and  is  reweighed.  The  difference  represents  volatile  oil. 

(<?)  Fiber  is  determined  as  on  page  180. 

Black  pepper  is  the  dried  unripe  fruit  of  piper  nigrum,  and  white 
pepper  is  the  dried  ripe  fruit  of  the  same  deprived  of  its  outer 
black  covering.  The  following  analyses  f  of  both  kinds  in  whole 
conditions  will  give  a  good  basis  of  comparison  : 


Water. 

Ash. 

Volatile 
Oil. 

Ether 
Extract. 

Starch. 

Crude 
Fiber. 

Whole  black.                  

8.15 

2.91 

1.48 

8.68 

33.92 

8.74 

Whole  white      

I  O.6o 

1.34 

1.26 

9.02 

43-10 

4.20 

*  U.  S.  Dept.  Agriculture  Bul'etin  No.  13,  p.  165. 
f  Bulletin  loc.  cit. 


Index. 


Acetone,  estimation  of  in  methyl  alcohol, 

107. 

Alcohol,  103,  107. 
Alumina  as  a  reagent,  90. 
Aluminium  acetate,  145. 
sulphate,  143. 

detection  of  iron  in,  143. 
Aniline  black,  161. 
Animal  charcoal  (see  Bone  black). 
Asphalt  and  asphaltic  substances,  172. 
analysis  of,  173. 
determination  of  asphaltene,  petro- 

lene,  water,  173. 
matter  not  bitumen,  mineral  matter 

in,  174. 
table  of  analyses  of,  1 74  • 

Baker  guano,  76. 

Beeswax,  examination  of  for  adulterants, 

122. 

determination  of  carnauba  wax, 
neutral  fat,  stearic  acid,  in, 
124. 

ceresin  and  paraffin  in,  123. 
specific  gravity  of,  121. 
total  acid  number  of,  122. 
Beets,  estimation  of  sugar  in,  82,  83. 
Bleaching  lime,  169,  172. 

materials,  153. 
Boiler-water,  20. 

analysis  of  according  to  Kalmann, 

22. 

determination  of  alkalies,  chlorine, 
sulphuric  acid,  carbonic  acid, 
nitric  acid  in,  21. 
ammonia  in,  22. 
total  solids,  silica,  ferric  oxide, 
alumina,  lime  and  magnesia 
in,  20. 

estimation  of  hardness  of,  23. 
preparation  of,  25. 
Bone  black,  76,  91. 

determination  of  carbonate  of  lime 

in,  92. 

sulphate  of  lime,  calcium  sul- 
phide, phosphoric  acid  in, 94.' 
water,  carbon,  sand  and  clay 

in,  91. 
Bone  meal,  76. 


Brine,  n. 

determination   of    lime,    magnesia, 

carbonic  acid  in,  12. 
specific  gravity  of,  1 1 . 
total  chlorine,  sulphuric  acid, 
ferric  oxide  and  alumina  in, 
II. 

qualitative  tests  for  potassium,  bro- 
mine, iodine  in,  12. 
Butter,  177. 

analysis  of,  177. 

determination   of    fat,    curd,    salt, 

milk  sugar,  water  in,  177. 
Butter  fat,  constants,  178. 
examination  of,  178. 

Cane  sugar,  estimation  of  by  inversion, 
80,85. 

by  means  of  specific  gravity,  79. 

by  polarization,  79. 
Camallite,  77. 
Castor  oil,  118. 
Chrome  alum,  145. 
Chromium  fluoride,  145. 

mordants,  145. 
Clay,  39. 

analysis  by  suspension,  43. 

calculation   of    refractoriness    from 
analysis  of,  49. 

determination  of  refractoriness   of, 

47- 

empirical-technical  analysis  of,  40. 
pyrometric  tests  for,  45. 
rational  analysis  of,  42. 
Coal,  coke,  etc.,  27. 

and  coke,  absolute  heating  value  of, 

3*. 

Cocoa  and  chocolate,  180. 

determination  of  water,  fat,  sugar, 
starch,    theobromin,   nitrogenous 
matter,  ash,  181. 
Coffee,  179. 

average  composition  of,  179. 
estimation  of  fiber  in,  180. 

water,  ash,  caffein  in,  179. 
Coke,  evaporative  efficiency  of,  32. 
Condensed  milk,  176. 
Copper,  crude,  60. 
mordants,  147. 


186 


INDEX. 


Crude  anthracene,  1 66. 
benzene,  165. 
carbolic  acid,  167. 
copper,  60. 

determination  of  antimony,  tin, 
arsenic  in,  63. 

bismuth,  6  $. 

iron,  nickel,  cobalt,  zinc  in,  62. 

oxygen,  phosphorus  in,  66. 

silver,  lead  in,  61. 

sulphur  in,  66. 

Dextrin,  154,  155. 

determination  of  acidity  of,  155- 
maltose,  starch  in,  155- 
water,  ash,  156. 
Dimethyl  aniline,  168. 
Dried  blood  powder,  78. 

meat  powder,  78. 
Drying  oils,  114. 

Maumene's  test  for,  115- 
Dung,  78. 
Dye-stuffs,  158. 

basic,  acid,  mordant,  159. 

direct    cotton,    "vat,"    diazotized, 
1 60. 

method  of  testing,  162. 

Farth  wax  (see  Ozokerite). 
Ela'idin  tests  for  oils,  115. 
Evaporative  efficiency  of  coke,  32. 

Fats,  109. 

determination  of  acid  number  of, 

"3- 

acetyl,  112. 

Hiibl's  iodine  number  of,  ill. 
Reichert-  Meissl  number  of,  117. 
saponification  number  of,  I IO. 
Fehling's  solution,  90. 
Ferro-chrom,  analysis  of,  70. 
Fertilizers,  72. 

determination  of  nitrogen  in,  74. 
phosphoric  acid  in,  72,  73. 
potassium  oxide  in,  73. 
mixed,  78. 
nitrogenous,  78. 
phosphate,  75. 
Filling  material,  84. 
Finishing  materials,  156. 
Fish  guano,  78. 
Flour  and  other  cereals. 

determination  of  water,  ash,  starch, 
nitrogenous  matter,  fat,  water  ex- 
tract, wood  fiber  in,  182. 
Food  stuffs,  174. 
Freezing  point  of  fatty  acids,  1 20. 


Fuel,  27. 

determination  of  ash,  sulphur,  total 

sulphur  in,  28. 
nitrogen,  phosphorus  in,  30. 
elementary  analysis  of,  29. 
Fuming  sulphuric  acid,  5. 

estimation   of  sulphuric   anhydride 

and  sulphurous  acid  in,  5. 
Furnace  gases,  32. 

Gas  oil,  131. 
Glycerin,  140. 

determination  of  in  fats,  141. 

soaps,  137,  141. 
Green  syrup,  84. 
Gums,  156. 

de  Haen's  salt,  146. 
Half- silk  fibers,  152. 

-woolen  yarns  and  fabrics,  152.  * 
Hardness  of  water,  determination  of,  24. 
Hide,  powdered,  78. 
Horn  meal,  78. 

Hiibl's  iodine  number  for  fats,  ill. 
Hydrogen  peroxide  and  permanganate, 
172. 

Ice  colors,  161. 

Illuminating  oils  (see  Petroleum). 

Indigo,  163. 

Ingrain  colors,  161. 

Invert  sugar,  80,  85. 

estimation  of,  85,  86,  87. 
Iron  pyrites,  I. 

determination  of  sulphur  in,  I. 

copper,  arsenic,  moisture  in,  2. 

Kainite,  78. 

Kottstorfer's  saponification  number,  no. 

Lead  acetate  as  a  reagent,  90. 
Lime,  35. 

determination  of   alkalies,   organic 

matter  in,  37. 
carbonic  acid,    oxide   of    iron 

and  sulphuric  acid  in,  36. 
moisture,    silica,    clay,    ferric 
oxide,    alumina,    lime    and 
magnesia  in,  35. 
saccharate,  91. 

estimation  of  sugar,  lime  in,  91. 

Malt,  loo. 

diastatic  value  of,  101. 
estimation  of  maltose  in,  101. 

water  in,  100. 
extract,  loo. 


INDEX. 


187 


Maltose    in    dextrin,  determination    of, 

155- 

in  malt,  determination  of,  101. 
Manganese  dioxide,  171. 

bleaching  lime,  etc.,  169. 
Marl,  37. 

determination    of     soluble     silica, 

coarse  and  fine  sand  in,  37. 
Materials  used  in  oiling  wool,  131. 
Maumene's  test  for  drying  oils,  115.. 
Mean  molecular  weight  of  fatty  acids, 

133- 

Meat  powder,  dried,  78. 
Methyl  alcohol,  107. 

estimation  of  acetone  in,  107. 
Milk,  174. 

analysis  of,  175. 

determination    of   albuminoids    in, 

177. 

milk  sugar  in,  176. 
solids,  ash,  fat,  casein,    albu- 
min in,  175. 
Mineral  lubricants,  126. 
acidity  of,  129. 

determination  of  flash-  and  burning- 
points,  specific  gravity  of,  128. 
resins,  fatty  oils,  rosin  oils  in, 

129. 

waxes,  125. 
Mixed  fertilizers,  78. 
Molasses,  84. 

Nickel  steel,  analysis  of,  71. 

Nitrogen,  determination  of  by  Gunning 

method,  182. 
Kjeldahl  method,  74. 
Nitrogenous  fertilizers,  78. 
Nitroso  acid,  7. 
Non-drying  oils,  1 14. 

Oil,  arachis,  119. 

castor,  1 1 8. 

fish,  114. 

olive,  117. 

rape- seed,  118. 

sesame,  118. 
Oils,  saponification  equivalent  of,    109, 

no. 

Orsat  apparatus,  32. 
Oxy  cellulose,  153. 
Ozokerite,  125. 

Pepper,  183. 

determination  of  water,  ash,  starch, 

fats,  fiber  in,  183. 
Persulphate,  154. 
Peru  guano,  78. 


Petroleum,  129. 

distillation  point  of,  1 10. 
determination  of  flash-point,  specific 

gravity  of,  129. 
viscosity  of,  130. 
Phosphor-bronze,  68. 

determination   of  tin,    phosphorus, 

lead  in,  68. 
copper,  zinc  in,  69. 

Phosphoric  acid  determination  of  in  fer- 
tilizers, 72,  73. 
Phosphorite,  76. 
Portland  cement,  38. 

composition  of,  38. 
Potassium  alum,  145. 
bichromate,  145. 
fertilizers,  77. 
nitrate,  78. 

Press  cake,  estimation  of  sugar  in,  91. 
Pyrites^ see  Iron  Pyrites), 
residuum,  3. 

determination  of  sulphur  in,  3. 

Raw  sugar,  84. 
Refined  copper,  60. 
Rendement  or  yield  of  sugar,  89. 
Resins  in  mineral  lubricants,  test  for,  1 29. 
Ritthausen's  method   for  determination 

of  milk  sugar,  176. 

Rosin  in  beeswax,  determination  of,  125. 
soaps,  detection  and  estimation  of, 
137- 

Saccharose  (see  Cane  Sugar). 
Shoddy,  152. 

Soaps,  determination  of  alkali   carbon- 
ates and  free  alkali  in,  135. 
free  fatty  acid,  neutral  fats  in, 

136.    ' 

glycerin  in,  137. 
rosin  in,  137. 
water,  total  fat,  total  alkali  in, 

*3S- 

solution,  preparation  of  normal,  23. 
Soda.  13. 

determination  of  moisture  in,  16. 
sodium  sulphate,  chloride,  hy- 
drate, sulphide,  sulphite,  sili- 
cate  and   aluminate,   bicar- 
bonate in,  15. 
total  active  soda  in,  14. 
qualitative  tests  for  sodium  hydrate, 

sulphide  and  sulphite  in,  14. 
quantitative  estimation  of,  14. 
Sodium  aluminate,  17,  145. 

estimation  of  soda  and  alumina 
in,  17. 


188 


INDEX. 


Sodium  bicarbonate,  145. 

nitrate,  78. 
Specific  gravity  of  solid  fats  and  waxes, 

determination  of,  116,  121. 
Spices,  etc.,  183. 
Spirits,  determination  of  alcohol  in,  103. 

fusel  oil  in,  104,  106. 
Stannous    chloride,     determination     of 

stannous  oxide  in,  146. 
Starch,  99,  157. 

determination  of  in  raw  products, 

95,  98. 
Sugar,  79. 

determination  of  ash  of,  8l. 
cane  sugar,  79. 
specific  gravity  of,  79. 
water  in,  80. 
estimation  of  alkalinity  of,  81,  88. 

"salts"  in,  8r. 
general    methods   of  investigation, 

79-. 

polarization  of,  79. 
quantitative  estimation  of,   79,  80 

84. 

Sulphuric  acid,  qualitative  tests  for  sul- 
phurous acid,  hydrochloric  acid, 
oxides    of    nitrogen,  lead,   iron, 
arsenic  in,  4. 
quantitative   estimation   of    arsenic 

in,  5. 
anyhydride  (see  Fuming  Sulphuric 

Acid). 
Super-phosphates,  76. 

estimation  of  total  phosphoric  acid 

in,  77. 
water-soluble  phosphoric   acid 

in,  77- 
Sylvite,  77. 

Table  for  invert  sugar  by  Herzfeld,  89. 

Killer,  90. 

milk  sugar,  176. 

of  analyses  of  coffee,  179. 

constants  for  common  waxes, 

I2q. 
German  degrees  of  hardness  of 

water,  25. 
iodine  numbers  and  saponifica- 

tion  numbers  of  fats,  113. 


Tallow,  120. 
Tanning  extracts,  148. 

estimation  of  water  and  ash, 
matter  soluble  in  hot 
water,  organic  matter 
insoluble  in  hot  water, 
non-tannins  in,  148. 
tanning  substances  in, 

149- 
materials,  147. 

raw  products  for,  149. 
Tartar  emetic,  147. 
Tea,  coffee  and  cocoa,  178. 

determination  of  moisture,  extract, 

178. 
theine,    caffein,    tannin,    ash, 

179. 
Thin  juice,  84. 

estimation  of  specific  gravity  of,  84. 

sugar  in,  84. 
Thomas  slag,  76. 
Tin  chloride,  147. 

salt  (see  Stannous  Chloride). 
Turkey- red  oil,  138. 

chemical  examination  of,  139. 
determination   of  solid  fatty  acids, 
ammonia  and  soda,  sulphuric 
acid  in,  140. 
total  fat,  neutral  fat  in,  139. 

Water  (see  Boiler- water). 
Waxes,  121. 

liquid,  114. 

mineral,  125. 

vegetable  and  animal,  1 21. 
Weldon  mud,  18. 

determination  of  manganese  dioxide 

in,  1 8. 
total  manganese,   "basis"  in, 

19. 

White  metal,  69. 
White  paint.  169. 

analysis  of,  169. 

scheme  for  analysis  of.  170. 
Wood  spirit  (see  Methyl  Alcohol). 

Xylol,  crude,  165. 
Yeast,  103. 


UNIVERSITY  OP  CALIFORNIA  LIBRARY 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


NOV   4  1916 
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APR  5  - 
REC'D  JLD 


30m-l,'15 


237357 


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